HITech

June 2012, Vol 1

HITech

Technical magazine of CSE Department, Heritage Institute of Technology

E d ito r : Pr of . R e s h m a R o ych oud h uri , A s s is ta n t Pr of es s o r, C S E

In This Issue: 1 . F or e w or d

Pa ge 2

b y Pr of. Par th a B a su ch owd h u r i, A s si st an t Pr ofes s or , CS E

2 . H a ck er s an d Sy st em S ec u r it y: A Ut i l it y -B ase d De c i s i on A n a ly s is M od el

Pa ge 4

b y Dr . Am it a va B a gc h i, Pr ofe ssor , C S E an d M r . S ou m y o D

M oitr a ,

R es ea r c h

S c ien tis t,

C arn e g i e

Me l l on

U n i v er s ity, Pitt sb u r gh , Pen n sy lva n ia, US

Pa ge 12

3 . E ss a y on A lan T u r ing b y F ir st Pla c e h old er of A lan T u r i n g Es sa y Wr i t in g C on te s t, M s. S at a ru pa G u h a, 4 t h Y ea r, BT e ch , C S E 4 . H a ve y ou e ver t h ou g ht wh at ot h e rs ar e

Pa ge 16

t h in k in g ?

b y D r. S u b h a sh is M a ju m d er , Pr of es s or an d H oD, C S E 5 . S y n ops is of " Em er g in g Tr en d s in A lg or it h ms " w or k sh op

Pa ge 19

b y Mr . S ou r a v D u t t a, 3 r d Y ear , BT e c h , C S E 6 . L i st of Pu b l icat ion s b y f a c u lt y a n d st u d en t s of C S E D e pa rt m en t of H I T [J a nu ar y t o J un e 2 0 1 2 ].

7 . A S i m p le U SB Devi c e D r iver on L i n u x p lat f or m s

b y Pr of. A r in d a m Ch at t e rje e, As s i st a n t Pr of e ss or , C S E

8 . S y n ops is of “ Fa u lt T oler a n t Sy st em s” w ork s h op b y Mr . K au st a v C h ou d h u r y, 1 s t Y e ar , MT e ch , C S E 9 . T e ln e t ove r S SL w it h Z -m od em

b y Mr . S ou m ab h o Ban er j ee, 3 rd Y e a r, BTe ch , CS E

Pa ge 21

Pa ge 22 Pa ge 27

Pa ge 32

1 0 . C r os sw ord

b y Pr of . R esh m a R oy c h ou d h u r i, As s i st a n t Pr ofe s s or, CSE

Dept. of CSE, Heritage Institute of Technology

Page 1

Pa ge 35

Foreword

Heritage

Institute

of

Technology

was

established by Kalyan Bharati Trust in 2001 at

B y P ro f . P a rth a Ba s u c ho wd hu ri , A s s i s tan t P ro f e s so r, CS E

Anandapur, Kolkata. In the depart ment of Computer Science and Engin eering, a team

"Computers ar e good at follow ing instru ct ions, but not at read ing your mind" - Dona ld E.

Dr. Knuth's quote suggests, exactly wher e the computer scient ists step in. Seeming ly their job is only to int er act with the comput ers But

their

cha lleng e

is

to

put

innovative featur es in a computer so that the computers can do whatever we th ink the computers can not do just yet - be it read ing one's mind or pred icting futur e. Simp ly put, the goal of studying a subject is to ma ke improvements subjects,

in

taught

th e as

f ield a

of

part

study.

of

a

The

degree

curriculum, are the build ing b locks of the computer science knowledge of a student. But unless this plethora of know ledg e is e xercised to successfully excute a hands-on project, justice is not done on the knowled ge at hand.

Open

forum

and

good

environ ment

for.

teacher-student int eraction can only increase the int ens ity, magnit ude and quality of the work. This is th e model that the depart ment of Computer Science and Eng ineer ing at Heritage Institut e of T echnolog y has been follow ing f or years.

The

faculty

members

have

been

work ing w ith the st udents hand-in-hand to strike the r ight balance for an excellent work ing

environ ment

and

to

produce

successfu l comput er scientists, eng in eers and entrepreneurs.

staffs work tir elessly with the students to g ive them a learning exp erience of int ernat ional

Knuth

eff iciently.

cons ist ing of thirty teaching and techn ical

standard.

Laboratories

updated

computers with high-end configurat ion adds to

that

exp erience.

department

have

Research ers been

from

pub lish ing

the t heir

orig inal w orks in top ranked in ternation al conferences and jour nals. Collaboration with elite

nationa l

and

internat ional

inst itut es

provides students the exposure to keep up with

th e

state-of-the-art

in

the

subject.

Workshops, seminars and presentat ions are organized to encourage in dependent r esear ch.

Students student

have chapter

recently to

for med

encou rage

an

ACM

t echn ical

activit ies with in the d epartment. The students organize technical events within th e inst it ute and also participate heavily in the techn ical events organized w it hin the inst itute as well as in other premiere academic inst itutes.

This department

year, of

for

the

Computer

first

t ime,

Science

the and

Eng ineering has taken the init iat ive t o pub lish a technica l magazine to p rimar ily encour age the students to hone their technica l writ ing skills. The pu rpose is not to publish f inal form of orig ina l research work but to revis it s ome areas of interest in the f ield of Comp uter Scien ce and b ring int o light various infor mal yet technical art icles. Senior faculty memb ers such as Dr. Amitava Bagchi, D r. Subhashis Majumder

Dept. Of CSE, Heritage Institute of Technology

with

Page 2

and

Arindam

Chatterje e

h ave

contributed en cou rage

w ith

techn ica l

origin a l

research

art ic les

to

be able to d raw inte rest of the re ad e rs as th ey

works

in

h a ve dra wn min e. N on et hele ss, th e e dit o r- in -

r esp e ct iv e fie lds. Un d erg ra dua t e a nd gra du a t e

ch ief

stu dents of fer t h eir mix of r ev iew a rt ic les a s

R oy c h ou dh u r i,

w e l l a s cu rs or y o r i g i n a l wo r ks . To ma rk A la n

P ro f ess or

Turing centen ary y ear, the ACM cha pter at

Sc ien ce a n d En gin ee r i n g, ha s p ut f o r w a rd he r

The

had

best ef fo rts to ma ke t h is ma ga zin e a succe ss

c on du ct ed a n es s a y c on t est th is y ea r. Th e

a nd I wou ld like to t a ke t h is op po rtu n it y t o

es sa y t ha t won t h e firs t pla ce in t h at con t est is

tha n k h er on beh a lf o f th e depa rt men t . Ot h er

a proud inclus ion. Oth er than that, sum ma ry

tha n edit ing, d i git a l t yp eset t ing a n d sev er al

of th e workshop o rg a nized by ACM chapt er

other tasks rega rdin g the f ormat ion of the

ha s a lso be en pu blis h ed . I s inc er e ly hope tha t

ma ga zin e,

the ra n ge of th e a rt i c l es p ubl is h ed

ma ga zin e is a te ch nica l c rossw ord pu zzle,

He rita ge In st itu te

of

Techn ology

in

th is

e dit i on of the techn ica l ma ga zin e will

of

the in

tech n ica l who the

her

is

ma gaz in e, also

dep a rtmen t

an

Assistant

of

Computer

a dd e dcon t ribut ion

to

the

wh ich adds th e e le m ent of fun and ga mes t o the t echn i ca l knowled ge.

Wish y ou a ll a good readin g!

Dept. Of CSE, Heritage Institute of Technology

Reshma

Page 3

Hackers and System Security: A Utility-Based

Decision

Analysis

Model By

D r.

an d

A m it a va

Bagc h i,

So u m yo

Sc ie n t i s t,

D

Ca rn e gi e

P ro f e s so r,

Mo i t r a, Me llo n

CSE

Re se a rc h Un i ve rs i t y,

P it t sbu rgh , P e n n syl v an i a, US

A bst ract: The best way for an organizat ion to respond to the menace of hacking can be determined us ing two differ ent approach es, namely decision analysis and game theory.

Under certain circumstances a game-theoretic may

provide

superior

strategic

alternatives in th e w ar against hackers. But game

theory

assumes

that

all

alt ernative

strateg ies available to the two antagonists are publicly known, which might not be true in rea lity. This paper presents a decision analysis framework where the hacker’s ut ility is made to depend on the degree of diff iculty in hacking, which can be expressed as a function of the organizat ion ’s secur ity paramet ers. We consider three types of hackers accord ing to their mot ivations, and mod el the expected utility H of a hypothet ica l compos it e hacker.

H

point F is a lways maximized.

Ar ea: Information Secur ity

M r.

solut ion

difficu lty level, to ensure that at the operating

determines

the

probab ility

of

hacking

through the Log it Model of qualitat ive choice, allowing us t o estimate the expected da mage in cur red by the organization as a result of hacking. If we also k now the cost of secur ity, we can derive the org anization’s ut ility F, a nd compare th e d ifficu lty levels at which H attains its minimu m value and F its maximum value. As the hacker’s profile changes, the organization

respon ds

by

modify ing

the

secur ity paramet ers and thereby changing the

1.Int roduction: Determin ing the appropr iate level of network security is an important issue for a ll organizat ions that make use of t he Internet. While inadequate security can cause great damage, excessive invest ment in secur ity is a waste of resources. We develop a decision analysis mod el t o help organ izat ions to decide on the optimal level of secur ity for their computer systems. We exp ress th is level in terms of common ly used security paramet ers, and

also

relate

it

to

the

not ion

of

t he

survivab ility of the system when attacked [Moit ra and Konda 2000]. The hacker’s ut ility and the organization’s utility can be viewed as funct ions of this level. Some recent stud ies [Cavusoglu

et

Raghunathan

al

2004,

2004]

Cavusoglu

and

adopted

an

have

interest ing game-the oret ic approach to the hacking p rob lem. These shed new light on t he issue

and

p rovide

network

administ rators

with mu ch needed d ecision p rocedures. But there is some uncertainty whether a game in the game-theor etic sense is being p layed at all.

An

organizat ion

is

interested

in

min imizing total ex pected cost, not in the equilib riu m point of a game. In fact, there is in complet e infor mation in this situation. For either player, the opponent’s ut ility cannot be known accurately, nor can the set of strategies available

to

the

opponent

be

known

comp let ely, violatin g a basic p remise of game theory. The feasib le set of strateg ies may actually b e qu it e comp lex. Also, th ere are hackers of many hues, so only a many-player

Dept. Of CSE, Heritage Institute of Technology

Page 4

mod el is really applicable. Sin ce this is a non-

illega l int rus ions. When an IDS alarm in

zero sum ga me, it is not st raightf orward to

conjunct ion with manual checks f inds t hat

find the equilibrium point. The s equence of

hacking has taken place, corr ect ive act ion is

moves needs to be specif ied, and this is not

in itiated

obvious a pr ior i.

satisfactory operation, the secur ity hardwa re

In our d ecision-theoret ic opt imizat ion model, we d erive express ions for the ut ility of t he hacker

and

probability

of of

the

organization.

hack ing

then

The

becomes

a

funct ion of the ut ilit ies of the hacker when hacking and when not hacking. We show that the

opt imal

level

of

secur ity

from

t he

organization’s point of view is not necessar ily at

the

point

wh ere

a

hacker’s

ut ility

is

minimized. We also show how this opt imal point changes as the security parameters and the prof ile of th e hacker change. A nume rical examp le illustrates the main featur es of the mod el

and

to

minimize

software

are

damage.

To

ensure

supplemented

with

appropriate ru les an d procedures. Ind ividual hackers have vary ing skills and resources. So, given a system S, the perceived deg ree of difficu lty in hack ing S varies with the hack er.

Of course, not a ll hackers are interest ed in hacking S. Wh en we ref er to the perceived degree

of

d iff icu lt y

of

S,

we

restr ict

cons ideration to th e set of hackers who are interested in hacking S. Let Δ be the perceived degree of diff iculty in hack ing S averaged over all hackers in th e set. Δ is a measure of the secur ity level of S; it is a posit ive r eal number in the doma in [0,1]. The organization installs a specif ic secur ity infrastructure to

2. The Level of Security: To ensure efficient

protect S ther eby sett ing the value of Δ. T he

operat ion, every mod ern organ ization makes

notion of the surviva bility σ of a system has

use of comput er resources. We ref er to the

been defin ed by Moit ra and Konda [2000] as

computer

“the d egr ee t o wh ich a system is ab le to

resources

of

an

organ ization includes

withstand an attack and still funct ion at a

software,

cer tain level at its new state after the attack”;

applicat ions software , Intern et websit es, and

σ is a rea l number in the domain [0,1]. Δ and

databases

The

σ are closely related and can in fact be

organization erects a security wall around the

id ent if ied; Δ looks at the system from t he

system to safeguard it fr om hackers. The

hacker’s

secur ity

organization’s p oint of view.

collect ively

as

the

computer

hardware, and

system.

systems

data

mechan isms

Th is

warehouses.

are

of

three

typ es:

prevent ive,

detect ive

and

correct ive.

prevent ive

mechanism

such

as

a

A

firew all

inhib its an unauthorized user f rom enter ing the system. A detect ive mechanism such as an Intrusion Detect ion

System

(IDS)

tracks

unusual

of

view,

and

σ

f rom

t he

3.The Hacker’s Utility: A hacker can have three d ist in ct reasons for hack ing: A.Monetary

gain

emb ezzlement,

or

information;

patterns of user beh avior to detect possible Dept. Of CSE, Heritage Institute of Technology

p oint

Page 5

through access

to

f raud,

confident ial

B.The menta l challenge of hack ing and a

Here, f1 + f2 + f3 > 1 always; since a hacker

desire to rise in t he est imation of ot her

can have more than one mot ive for hack ing, it

hackers;

is possib le that

C.Political or r eligiou s animosity towards t he

f1

organization b eing attacked.

H1 H H  0, 2  0, 3  0    .

In hacking of type A, the utility H of the

+

f2

+

f3

>

1.

We

know

th at

hacker decreases as the diff iculty level Δ

It follows that H varies with Δ as shown in Fig

in creases; in hacking of type B, H increases as

1. We expect this variat ion to be non- linear,

Δ in creases; and in hacking of type C, H does

and the value of H to be h igh both when Δ is

not depend on Δ.

small and when Δ is larg e. H is min imum at

Let

us

consid er

a

hypothetica l

“compos it e” hacker w ho has all th ree mot ives for hack ing S in the proport ions given b elow.

In a particular situation, she can choose to

the point Δ = Δ1. If the organ izat ion is able to set Δ to Δ1, the hacke r has the least incent ive to engage in hack ing. Possib le funct ional forms for H1, H2 and H4 are

hack or not to hack. When she does not hack, she

has

an

expected

ut ility

H0

that

H1 

is

independent of Δ. Wh en she hacks she has an

H 4  a '' b " 

expect ed ut ility H = f1H1 + f2H2 + f3H3 wher e H lies in the domain (- ∞, +∞) and

1 , H2  a '   b ' 2 a  b , ,

where a, b, a’, b’, a”, b” are posit ive constants

f1 is the p rop ort ion of hackers of type A (in

and 1 < ε < 2.

the set of hackers attack ing system S) Hacker's Utility (H)

18

f2 is th e proportion of hackers of type B

14 H 10a

f3 is th e proportion of hackers of type C

c

k

e

r

'

6 2 -2 -6

H1 is the ut ility of a hacker with mot ivat ion A

0

4

8

Secu rity Lev el (Δ)

12

alone H2 is the ut ility of a hacker with mot ivation B

Fig 1: Variation of H with Δ

alone H3 is the ut ility of a hacker with mot ivat ion C alone

1.0 d

0.5

0.0 0.0

Dept. Of CSE, Heritage Institute of Technology

Page 6

0.5

1.0

Fig 2: R OC Curve for Firewall

another real constant > 1. This also def ines an

4. Functional Form for Δ: We would lik e to express Δ as a function of the six princip al secur ity paramet ers [Cavusog lu et al 2004]:

ROC cu rve, and a figure of mer it for the I DS is dI, the closest distance this curve approaches the point (0,1); dI is a function of s. Since the diagonal in the ROC curve has a length of √2,

q1F the probab ility that the firewa ll stops an unauthorized user

q2F

we

the probability that authorized external

traffic passes th rough the f irewa ll

q1I

when an int rusion occurs

alarm wh en th ere is no int rusion of

probab ility

monitoring

of

manually

monitoring

manually

well kn own that in a firewa ll, the paramet ers F 2

q and q are re lated by an equation of th e form

1  q2F   q1F 

, wher e r is a constant > 1

the relat ionship is called an ROC curve ([Metz 1978], see Fig 2). We would like th e f irewall to operate at the point (0,1) in the graph, i.e.,

qF qF at the top left corner where 1 = 2 = 1, but in pract ice it can operat e only at a point on the ROC curve. A f igur e of mer it for th e f irewall is dF, th e closest d istance the R OC curve approaches the point (0,1); clearly, dF is a funct ion of r. Similarly, for the IDS, t he

q1I

the

and

equation of the form

q2I

are

related

1  q2I   q1I 

Dept. Of CSE, Heritage Institute of Technology

secur ity

inf rastructure,

to

vary

t he

and manual che cking to the value of Δ. T he close r a produ ct t erm gets to 1, the hard er it ignored

because

in

practice

there

is

of IDS alar ms. If we want to incorporate it, we can includ e an addit ional product term of the form

by

an

s , where s is

1  2 t

'

, where t’ is another pos it ive

constant.

r

[Yue and Bagchi 2003]. The graph that shows

parameters

want to assign to the diff er ent components of

frequent ly no manual check ing in the absence

when the IDS does not produce an alarm It is F 1

and tF, tI and t are also posit ive constants that

is to hack S. The cont ribut ion of ρ2 has been

when the IDS produces an alarm ρ2the

where c is a posit ive scaling constant,

re lat ive cont r ibut ions of the f irewall, th e I DS,

q2I the probability that the IDS generates no

probab ility

write

t dI  I t  . 1   .1 2 

can be adjusted, depending on the weigh ts we

the probability that the IDS gives an alar m

ρ1the

can

t  dF  F   c.  1   2 

To determine dF we f irst min imize the expr ession y2r+(y-1)2 with respect to y where y is a positive real variable, and then take the square r oot. Assuming r = 5, this yields dF = 0.340 and (1- dF/ √2) = 0.725; s imilarly, assuming s = 10, we get dI =0.226 and (1dI/√2) = 0.841.

5.The Utility of the Organization : The utility F of the organizat ion can be expressed in t he form F = F1 + F2 wh ere F, F1 and F2 are all negative and dep end on Δ. Here, -F1 is a measure of the expected damage caused by hacking and -F2 is t he cost of the secur ity infrastructure.

Page 7

We can write F1 = -P.D, where P is the probability that hacking occu rs and D is the expect ed damage. To obtain an expression for P

we

make

Qualitative

use

of

Choice

the

Logit

[ McFadden

Theory 1980,

of

Ben-

Akiva and Lerman 1985, Train 1986]. This theory is based on the concept of ut ility and has been extensively applied to situat ions in which a person chooses one option from an exhaustive f inite set of mutually ex clus ive

F 0 at Δ = Δ2. Using the realist ic that  funct ional f orms D   e

home to a specif ied dest ination. In our case the

hacker

opt ions,

to

has

two

hack

or

mutually not

to

ex clusive

hack,

with

cor respond ing utilit ies H and H0. By the Logit Theory,

eH P  H0 e  eH .

P H is always posit ive

when H is f inite, so P varies with Δ in the same manner as H. The expect ed da mage D decreases as Δ increases. Thus F1 varies with Δ as shown in Fig 3. Since -F2 incr eases as Δ in creases, F varies with Δ as shown. F is maximu m at the p oint Δ = Δ2, and the organization wou ld want to operate at t his point.

For a given set of parameter values, the F-Δ curve remains fix ed for an organization . Δ changes as the security level is adjusted, and the operating point moves along the F- Δ cu rve to a new posit ion. If the operat ing point is to the r ight of Δ2 the system is over-secu re a nd Δ should be decreased; if it is to th e left of Δ2 the system is unde r- secure and Δ should be in creased.

and

F2   e  ,

P  (    )  P e  get  at Δ = Δ2. Cavusog lu et

al

[2004]

implicit ly

assume

that

t he

parameters β and μ are both zero; this makes

P H  = 0, which imp lies  = 0 and forces Δ1 =

P Δ2. In our mode l we allow  ≠ 0 at Δ = Δ2.

If

the

second

t erm

in

the

RHS

of

t he

P P expr ession for  exceed s the first, then  < H 0, implying  < 0. Th is can be t rue only for values of Δ less than Δ1; thus, Δ2 < Δ1.

Simila rly, when the second t er m is smaller than the first, Δ2 is greater than Δ1. The system operates at Δ = Δ2, which for ces the hacker to op erate at the same point (Fig 3).

Thus the hacker’s utility is not necessarily at its lowest at Δ2 but can be somewhat larger.

7.Tuning the System Security: If the system is operat ing at Δ = Δ2 and all paramet ers remain unchanged, then it is in a stable state and no adjustments in the secur ity set-up are needed.

Ther e

are

two

s ituations,

how ever,

when

secur ity tuning might be required. In ord er to plot the H-Δ curve, th e parameters fk, 1 < k < 3, must f irst b e est imated. By an examination of th e user log files of S, we can in theory

Dept. Of CSE, Heritage Institute of Technology

 

where α, β, γ and μ a re posit ive constants, we

alternatives, as for e xample when buying a car or when s elect ing a travel route from

Relative Va lues of Δ1 and Δ2: We know

6.

Page 8

id entify the p roport ions of hacking act ivity of

Step 1:

System websit e or database gets

types A,

changed, or better estimates of fk become available.

50.0 Δ1

H

0.0 0

5

10

15

Δ2

-100.0

H-Δ

is

curve

Step 4: Security Level (Δ)

The

(new

Δ1

is

With the h elp of the P- Δ p lot, the

new F-Δ curve is plott ed.

Step 5:

3:

afresh

plotted against Δ.

F

-200.0

Fig

p lott ed

Using the new H- Δ curve, P is

Step 3:

F2

-150.0

Hacker’s prof ile changes, so the

obtained).

F1

-50.0

Step 2:

Utility

Function

F

and

th e

Operating Point Δ2

The new operating p oint Δ2 of

the system is det ermin ed. At this p oint t he new F has its maximum value. This is also the new op erating point of the hacker.

8. Numerical

Example:

We

illustrate

our

B and C. The numb er of b reak- in attempts at

mod el w ith a numerical example. Since not

any given organizat ion might not be large, so

much rea l lif e data on hacking is pub licly

to get larger samp les for est imation w e can

available, we make use of hypothet ical but

classify

and

realist ic data. For Ta ble 1, we have assumed

estimate the values of fk, 1 < k < 3, from t he

the following paramet er va lues: f1 = 0.6, f2 =

totals for each category. If more extens ive and

0.3, f3 = 0.1, H0 = 1, H3 = 50, α = 2000; β =

reliable data become available at a later time,

0.5; γ = 50, μ = 0.1, ε = 1, a = 0.001, b = 0.003,

the est imates can be revised. Chang ing t he

a’ = 0.7, b’ = 0.9, a” = 2, b” = 35. Tab le 2 uses

fk’s would in effect change the expr ession for

the

H,

parameters as ind icated.

organizat ions

which

means

into

the

categor ies

H-Δ

curve,

and

same

consequent ly the F- Δ curve, would have to be redrawn. A s imila r s ituation ar ises when t he

va lues

bu t

var ies

Δ

database is alt ered. T hat would, over a period thereby changing the fk va lues. In summa ry,

of

t he

f2.H f1.H1

2

H4

H

P

content or format of the system website or of t ime, attract a different mix of hackers,

some

46.

4

2

5.2

F1

F2

F

-

-

-

4

13.

0.3

80.

74.

154.

3

3

0

1

6

7

5.3

0.2 8

-82.4

128.3

the steps in t ime sequence in the decis ion process are as follows: 5

Dept. Of CSE, Heritage Institute of Technology

Page 9

37.

5

7.8

45

-45.9

6

31.

6

11.

0

0.6

0.2 7

-26.9

-91.1

118.0

7

27.

3

14.

7

-2.0

0.2 6

f2 high

0.2

0.7

0.1

2000

50

4

6

-16.0

100.7

116.7

f3 high

0.3

0.2

0.5

2000

50

9

7

8

24.

0

19.

0

-3.0

0.2 6

120.9

Base case – new α

0.6

0.3

0.1

1000

50

8

6

-9.6

111.3

9

21.

4

23.

8

128.8

Base case – new γ

0.3

0.1

2000

200

8

5

-5.9

123.0

0.6

-2.8

0.2 6

53

1 0

19.

4

29.

1

55

-1.5

0.2 7

-3.6

135.9

139.5

Ta b l e 2 : S e n si t ivi t y o f Δ1 a n d Δ 2 w i th r e s pec t t o si g ni fi ca n t m o de l pa r a m e ter s

1 1

17.

6

35.

0

57

0.6

0.2 7

-2.2

150.2

152.4

Table 2 shows how Δ 1 and Δ2 change as

1 2

16.

2

41.

4

59

3.6

0.2 8

-1.4

166.0

167.4

particular the pr oportions fk, 1 < k < 3, the

1 3

15.

0

48.

4

61

7.4

0.2 8

-0.9

183.5

184.3

We f ind that Δ1 is much more sensitive to

47

49

51

f1 high

0.8

0.1

0.1

2000

50

16

7

some

of

the

paramet ers

are

varied,

in

coeff icient α of D and the coefficient γ of F2. changes in fk, 1 < k < 3, than Δ2. However, Δ2 is more s ensitive to variat ions in the

Ta b le 1 : V ar i a ti o n o f H a n d F w i t h Δ

Table 1 shows that the hacker’s ut ility is relat ively high at a low secu rity level. But as the security level increases, the utility fa lls, going b elow the base level H0 (in the interval 0.6 < Δ < 1.1) and even becoming n egative.

damage and cost coeff icients than Δ1, as would

be

exp ected.

We

might

want

to

compare the value of Δ at the equilibrium point achieved und er the assumpt ions of game theory to the values of Δ1 and Δ2 comput ed

When the secu rity level increases further, t he

using ou r method.

utility rises again. Thus in some situat ions the

9.Conclusion: In this paper we have tried to

hacker’s ut ility is high er when she is not hacking than when she is hack ing. Simila rly, at

low

security

levels,

the

organization’s

utility has a relatively low value. It rises to a higher value as the security level increases, but

falls

as

the

security

level

increases

further. The point at which the hacker’s utility is lowest does not coin cide with t he point at which the organization’s ut ility is highest (N.B. Δ1 = 0.8, Δ2 = 0.7. so Δ1 > Δ2). f1

Base case

0.6

f2

0.3

f3

0.1

Coef of D (α)

Cost coef (γ)

Δ1

2000

50

8

enumerate the d ifferent reasons for hack ing, and then model a ut ility function hypothetical

“comp osit e”.

for a

hack er.

T he

parameters of this utility funct ion can be interpret ed in ter ms of hacker mot ivations, and the probability of hackin g can b e d erived from it. We have also proposed the concept of “the degree of d ifficu lty in hacking” a g iven system and expressed it in ter ms of the secur ity parameters of the system. Fina lly, we

Δ2

have developed a u tility funct ion for t he organization

7

in

te rms

of

its

secur ity

parameters and show n how the organization can deter mine the level of security that is b est

Dept. Of CSE, Heritage Institute of Technology

Page 10

for itself. A numer ical example illustrates h ow

Metz C E (1978), Basic Principles of ROC

the opt ima l level of secur ity changes with key

Analysis, Seminar in Nuclear Medicin e, 8,

mod el paramet ers.

283-298

R eferences:

Moitra S D and Konda S L (2000), The Survivability

Ben-Akiva M and Lerman S R (1985), Discr ete

Emp irical

Choice Analysis: Theory and Application to

(2004), A Model for Evaluating I T Security

Raghunathan

S

R eport

Carnegie-Mellon

Theory, Economet r ics and an Applicat ion to Aut omobile Demand, MIT Press

(2004),

Conf igu ration of Detect ion Software: A Comparison of D ecision and Game Theory Approaches, D ecis ion Analysis 1, 131-148

Yue

W

and

Bagchi

Informational

Asset s

A

(2003), with

Protect ing

Firewa lls

at

Minimu m Cost, Proc WITS-2003, Works hop on

McFadden D (1980), Econometric Models of

Information

Technology

and

Seattle, WA, Dec 13-14, 2003, 31-36

Probab ilist ic Choice a mong Products, Jr of Business, 53, 513-529

Dept. Of CSE, Heritage Institute of Technology

Technical

An

Train K (1986), Qualitative Choice Ana lysis:

Investments, Comm ACM, 47, 87-92 and

Analys is,

Systems:

University

Cavusog lu H, Mishra B and Raghunathan S

H

Network

CMU/SEI-2000-TR-021,

Predict Travel Demand, MIT Press

Cavusog lu

of

Page 11

Systems,

Alan

Turing

Essay

Writing

Scient ific Specia list, h e is wasting his t ime at

Contest

a Public School.”

F i rst P lac e H o lde r, M s. S at a ru p a Gu h a, 3 r d

However, he won every possib le pr ize for

Y ea r, B Te c h, CS E

On a serene morning of June, 1954, a halfeaten apple lay besid e a man, convict ed of t he death of the father of comput er science, Alan Tur ing. His d emise, b elieved to b e the result of cynanide

poisonin g,

was

a

rather

b leak

accolade for the man who happened to be one

mathe matics while at school, and learnt deep mathe matics on h is own. He f ound specia l interest in Chemistry too and carried out selfdesigned

experiments

which

gr eatly

disp leased his t eachers. Flow ering under t he str ict

d iscouragement

of

his

inst ructors,

Turing cont inued

of the g reatest p ioneers of the computer f ield.

undeterred to spread himself int o the more

Mathematician,

crystanalyst,

prolif ic rea lms of scientif ic knowled ge. While

computer scient ist : Alan Tu ring encompassed

still being a school student, he had a lready

an wider spectrum of proficiency than that

read

procla imed by these f ew mere tags.

Eddington’s quantum mechanics. Not on ly did

Born

of

Br it ish

logician,

parents,

Ju lius

Mathison

Tur ing, memb er of t he Indian Civil Service, and Ehel Sara Stoney, on June 23, 1912 in

Einstein’s

papers

on

relat ivity

and

he grasp them, he even extrapolated Einstein’s quest ioning of Newton’s laws of mot ion fr om a text in which this was never made elicit.

England, Alan Tur ing was admitt ed to St.

Thankfully for Turin g, Cambr idg e prove d to

Michaels at the age of s ix and later to

be a better p lace to fit in for unconvent ional

Sherbourne School. From the very onset of his

people like h im. Entering into King’s College,

school education, he showed signs of gen ius

Camb ridg e to study mathematics, he could

and an unabashed int er est for science in

now

general, amd mathematics in part icular. His

mathe matical

first day of ter m coincided with the 19 26

developed a penchant for recreating th e works

General Strike in B ritain, but so det er mined

of previous scient ists. He proved th e cent ral

was he to attend th at he rode h is b icy cle

limit theorem, desp it e the fact that he had

unaccompanied more than 60 miles to sch ool,

failed to f ind out that it had already been

stopping overn igh t at an inn. However when

proved

it came to skills of the right brain, he suffered

dissertation earned him th e honou r of being

miserably.

elect ed a fellow at King’s in the same year.

He

was

crit icised

for

his

handwriting, struggle d at English, so much so that his headmaster once wrote to his mother:

seamlessly

in

pursue

log ic.

It

1922

his was

by

interest here

that

Lindenberg.

in he

This

In his path-breaking paper “On Computable Numbers,

with

an

Applicat ion

to

the

“If he is to stay at Public School, he must aim

Entscheidungsp rob lem” (submitted on 28 M ay

at becoming edu cated. If he is to b e solely a

1936) Turing reformu lated Kurt G ödel’s 19 31 results

Dept. Of CSE, Heritage Institute of Technology

Page 12

on

the

limits

of

proof

and

computation,

rep lacing

Gödel’s

universal

arithmet ic-based for mal language with what

of prob lems that cannot be solved by a Turing mach ine.

became renowned as Turing machines. He proved that such a simp le for mal machine would

be

capable

of

performing

any

conceivable mathematical computation if it cou ld be rep res ented as an algorith m. Perh aps the most r emarkable feature of Turing’s work on

Turing

mach ines

was

that

he

was

describ ing a modern

During the Second World War, Turing was a leading part icipant in th e b reak ing of German ciphers at Bletch ley Park, th e s ite of the

Unit ed

King dom’s

establishment,

th e

ma in

Government

de cryption Code

and

Cypher School, wh ere ciphers and codes of several

Axis

countries

were

decrypted.Turing’s brilliant id eas in solving

computer before technology had reached the

codes, and developing computers to assist

point

realistic

break them, may have saved more lives of

proposit ion. He went on to p rove that ther e

military p ersonnel in the cours e of the war

was no solution to the Entscheidungsp rob lem

than

by first show ing that the halt ing problem for

mathe matician

Tur ing mach ines is undecidab le. A lbeit, his

developed th e ‘Bomb e’, a mach ine based on

proof was published after Alonzo Church’s

earlie r work by Polis h mathemat icians, which

equ ivalent

from late 1940 was decod ing a ll messages

where

constr uct ion

was

proof, T ur ing

was

a

unaware of

From 1936 to 1938 he was actively res earch

Advanced Chur ch. played

work

Study, While

with

at

the

Pr inceton, at

the

Institute und er

Princeton, id ea

of

for

Alonzo

Turin g

had

const ructing

a

computer. Once back at Cambridge in 1938 he started

to

build

an

other.Together W

G

with

another

Welchman,

Turing

sent by the Ger man ‘Enigma’ mach ines, which

Chur ch’s wor k at th e time.

doing

any

analogue

mechan ical

device to investigate the Riemann hypothesis, the biggest unsolved prob lem in mathemat ics.

In addit ion to his pu rely mathemat ica l work, he studied cryptology and also built thr ee of four stages of an elect ro-mechan ical b in ary mu lt iplie r.In June 19 38 he obtained his PhD from Princeton.His dissertation (Systems of Logic Based on Ordina ls) ushered in the concept of ordinal logic and the notion of relat ive computing, where Turing mach ines are augment ed w ith oracles, allowing a study

Dept. Of CSE, Heritage Institute of Technology

could generate a constantly changing code that was imp ossible for the code b reakers to decipher in a t imely fashion. In July 1942, Turing devised a techniqu e termed ‘Tur ing ery’ for use against th e Lorenz cipher messages produced

by

Geheimsch reiber

the (secre t

Germans’ wr iter)

new

mach ine.

Turing and his fellow scient ists worked with a device

called

COL OSSUS.

The

COLOSSUS

quick ly and efficient ly deciphered th e German codes. COLOSSUS wa s essent ially a bunch of servomotors and metal, but it was one of the first steps toward the dig ita l computer.Turing travelled to the Unit ed States in Novemb er 1942 and worked w it h U.S. Navy cryptanalysts on Naval Enig ma and bombe const ruct ion in Washington, and assisted at Bell Labs with the development of secu re speech devices.

Page 13

After Wor ld War II, Turing took up long

that still plagues artificial int ellig ence today.

distance runn ing as a means of relieving t he

He w rote a paper in 1950 descr ibing what is

stress that he had

now known as the “Turing Test. ” The t est

been expe riencing lately and rea lised that he actually excelle d at it. He obtain ed record times in b oth the 3 and 10 mile races in t he Walton Athlet ic Club. Typical

cons isted of a person asking quest ions via keyboard to both a person and an intellig ent mach ine. He believed that if the person could not tell the machine apart from the person after

a

reasonable

amount

of

time,

the

of h is log ical nature, his somet imes used his

mach ine was somewhat intelligent. This test

athlet ic ability to run between locations for

has become the ult imate test of the art if icia l

his lectures.

inte lligence communit y.

Tur ing went on to work for the National

An aspect of h is life that most often re mains

Physical

unacknowledged

Tur ing went on to work for the National Physical Laboratory (NPL) and worked on developing the Automatic Comput ing Engin e (ACE), one of the f irs t attempts at creat ing a true digital computer. It was during th is t ime that he began to explore the relat ions hip betwe en computers and nature. He wrote a paper called “Int elligent Machinery” which was later pub lished in 1969. This was one of the

f irst

t imes

the

concept

of

art if icia l

int ellig ence was raised. He on ce joked“No,

I’ m

not

powerfu l

interested

bra in.

All

I’m

in

developin g

after

is

just

a a

mediocre brain, something like th e Pres ident of the American Te lephone and Teleg raph Company.”

Tur ing created

that

would

mach ines

cont ribut ion

to

Biology. By 1951 he was working on the applicat ion

of

mathemat ica l

theory

to

biolog ical forms. In 1952 he pub lished t he first

part

of

his

theoret ical

study

of

morphog enesis, the develop ment of pattern and

form

in

living

interested

in

how

developed

part icu lar

organisms.He

and

why

shapes.

was

organisms There

are

millions of cells in a person or a tree, and yet all know what shape to be. Tu ring yearned to unravel th is mystery.

Alan Tur ing would probably have laughed off the idea of being a philosoph er. He called himself a mathemat ician. But his 1950 paper ‘Comput er mach iner y and Intelligence’ has become one of the most cit ed works in mod ern

ref lect

the

be

mathe matical concept of computability into

int ricate

tradit ional prob lems of mind and body, free-

could

processes of the human brain. He d iscussed the

his

philosophica l lit erature. He brought the new

b elieved that

is

poss ibility

of

such

machin es,

acknowledg ing the diff icu lty peop le would have acceptin g a machine that would pos e a threat to their own int ellig ence, a prob lem

Dept. Of CSE, Heritage Institute of Technology

will and determinism.

A

victim

prejudice, house

of

social

Alan

arrest

stigma

Tur ing

and

was

forced

to

and

relig ious

p laced take

under regular

oestrogen injections after being convict ed of

Page 14

homosexuality, then a punishiable offence

went awfully wrong. Whatever the reason be,

under B rit ish law. He is believed to have

his death went on to resonate some of his own

brought death upon himself at the age of 41

words-

through a self-administered dose of p oison, although h is mother mainta ined that his death was caused by a chemical exper iment that

Dept. Of CSE, Heritage Institute of Technology

â&#x20AC;? Science is a differentia l equat ion. Relig ion is the boundary cond it ion.â&#x20AC;?

Page 15

Have

you

ever

thought

what

others

to

anticipate

he r

next

move.

A

others are thinking?

badminton p layer will pract ice hard to ensure

B y Dr. Su bh a s hi s M aju md e r, P ro f e s s o r an d

possible, whether she is h itt ing a drop or a

H o D, C SE

that her body action remains as similar as toss or a smash. This will give h er opponen t a

The answer to this question is defin itely yes,

fract ion of a second less to p red ict where her

but the more pert inent quest ion is how much

next shot w ill g o. Somethin g very s imilar was

or to what ext ent. Unless one can read others’

observed

minds at least to some extent, even s imple d ay

military st rateg ist in his famous treatis e ‘T he

to day operations will not prog ress. Take for

Art of War’, “… when able to attack, we must

examp le, when the cars are passing throu gh

seem unable; wh en using our forces, we must

an unmanned crossin g, wh ich does not ha ve

seem inactive, when we are n ear, we must

any traffic lights, f requent collisions would

make the enemy believe we are far away…”.

have

not

As your compet it or might be thin k ing so ma ny

pred ict what other drivers are going to do.

things, you also need to think what she is

They do so by judging the speed of the car, t he

think ing

lane in which the car is approach ing, t he

compet it ion of t oday’s corporate world.

happened,

if

the

drivers

could

angle at which the ca r is kept when it stopped at

the

crossing;

somet imes

an

eyeball

int eract ion among th e d rivers also h elps in the p rocess.

by

Sun

if

Tzu,

you

the

have

great

to

Chin ese

survive

the

I would lik e to ment ion some excerpts fr om Sun

Tzu’s

general

another

who

w ins

famous a

quote

battle

“…the

make

many

calcu lations in h is temp le …. The genera l who

Reading others' mind is extr emely important if

loses a battle makes but few calcu lations

you have to survive in games or sports. A

beforehand. Thus do many calculations lead to

batsman

correct ly

victory and few calculations to defeat. …”. In

whether the next ball is going to b e a bouncer

most of our rea l life situations also, failu re to

or a slower, has alr eady made her job much

plan is same as planning for failu re. You may

easier. While taking a penalty in foot ball, t he

have conceived one of the best products t hat

shooter is t rying to pred ict wh ich sid e t he

are possib le in a particu lar domain, but unless

goalkeeper is going to dive and the goa lkeeper

you

on the other hand is trying to f igure out

compet itor

which side the shot will come. Players t ry to

similar in a lesser t imef rame, you may be

observe very hard the body languages of their

risk ing

opponents, wher e they look or what els e they

pushing your R&D t eam to implement it.

who

has

anticipated

do befor e the crunch action if that can g ive the slightest clue about what is going to come next. Now, if there is espionage, there will be counter-esp ionage. So, a good player will always try to strategize how she can stop Dept. Of CSE, Heritage Institute of Technology

successfully can

your

evaluate come

up

company’s

whether w ith

future

your

something a

lot

by

Ther e are nu merous such examp les that led to the failure of very established technology companies b ecause of wrong st rateg ies. Now, how will you know w hat your comp et itors are

Page 16

They are not going to tell you f or

type of the puzzle. All my f riends with whom I

sure. That’s where comes in the power of

shared it later, appreciated its specia lty. I

think ing by the top strateg ists. You need to

admit I came across very few such pu zzles

figure it out from the symptoms that are

that make you think what other peop le are

availab le.

think ing.

doing?

The

in vestments

that

your

compet itors are making over the years, the me rg ers

and

acquisit ions

that

your

compet itors are going through might g ive

Puzzle : In a village t here are some villag ers

point ers to what you a re look ing for.

who are squint-eyed (tera). The prob lem is to

Given that we have spent enough efforts to mot ivate

our

top ic,

the

mor e

import ant

quest ion to answer is whether it is possible to

determine who the squint-eyed p ersons among the villag ers are. Now the re are some g iven cond it ions you have t o assume.

train oneself to successfully think in advance

1) A villager can never know wheth er she

what others are thinking. Modern psychology

herself is squ int-eyed (assume that there are

must have some answers but that is not my

no mir rors and there is no lak e where she can

cup of t ea. On a differ ent not e, I would

see her face).

ment ion the name of a book here – ‘Men are from Mars Women are from V enus’, wh ich is a must read for a ll would be husbands and wives and maybe usef ul also for the vet erans.

It will t each you or at least g ive you a few

2) A villager can see whether another villager is squint- eyed or not, but they cannot or are not

allowed

to

communicate

among

themselves by any means.

important tips about how the other gen der

3) All the villagers of that village know t hat

thinks – a very imp or tant knowledge t o avoid

there is at least one villager who is squin t-

collis ions on the road of Lif e. As a comp uter

eyed.

scient ist, I would suggest to read a few initia l pages from any good book on randomized algorith ms. There is a concept of adversary, and in your a lgorith m you try to strategize in a randomized fashion so that your phantom adversary cannot guess what you are going to do next. I will be brief here as I do not want to turn this into a lecture in algorith ms.

However,

it

is

def init ely

step

will go and stand in a queue say at 10:00 AM every morn ing and all of th em will be ab le to see each other. If at the end of the day anybody is sure that she herself is squinteyed, she should step out of the queue say at 6:00 PM.

toward

If nobody steps out, t hen all the village rs will

stopping other people from anticipating your

again stand in queue next morning and t his

thoughts. I will f in ish this with a puzzle that I

will cont inu e. So this process cont inu ed and it

came across in the f inishing days of my school

was found that suddenly at the end of a

lif e. Solving it gave immense p leasure no

cer tain day (say 40th), some villag ers came

doubt but what really attracted me was the

out together and it was found exactly those

Dept. Of CSE, Heritage Institute of Technology

a

Now a protocol is d ef ined. All the villag ers

Page 17

villag ers who were sq uint-eyed came out. T he

Note: The answer w ill obviously come in t he

question is â&#x20AC;&#x201C; how was this possible? Can you

next newsletter. However, if you are impat ient

t ell - what was the numb er of villagers who

to get your answer verif ied, please write to me

w ere squint-eyed? Explain your answer.

your exp lanation cle arly. I am available at :

Hint: To solve this puzzle, you have to assume

subhashis.majumder@heritageit.edu

that the villagers w ere quit e intelligent, at least intelligent enough to solve th is puzzle.

Dept. Of CSE, Heritage Institute of Technology

Page 18

Computer Aided D es ign techniques that have

Emerging Trends in Algorithms S y n o p s i s by M r. So u rav Du tt a, 3 r d Ye ar, B Tec h , CSE

The ACM stud ent cha pter in association with the

Department

of

Comput er

Science

of

Her itage Inst itute of Technology organ ised a two day refresher cou rse on 27th and 29th of February,

2012.

It

was

the

first

event

organised by A CM student chapter after its formation in January 2012.

field of Algorith m design. It was a huge success as it saw participation fr om both and

attendees

from

faculties. both

More

Her itage

than Inst itut e

100 of

Technology as well as from other colleges attended the two da y long event. The k ey speakers were Dr. Bh argab Bhattacharya, Dr. Susmita Sur- Kolay, Dr. Mandar Mitra and Dr. Subhas

Chandra

Nandy,

called

labonach ip,

which

is

capable

of

chemica l analysis or med ical d iagnosis. Th ese ch ips are likely to bring a comp lete parad igm shift in the area of biochemical diagnost ics, DNA detect ion, or drug design system, to name a few. Dr. Bhattacharya has a fathom research experien ce on nano bioch ips and during the refresher course, he spoke about several a lgor ithmic issues of design and t est

The event focused on the new t rends in t he

students

enabled the develop ment of a t iny device

all

f rom

Indian

of a dig ital microf luid ic b iochip and their impact on various r eal lif e situations.

Dr. Susmita Sur-Kolay shared her knowledge on Elect ron ic

D esign

Automation

for

VLSI

physical des ign, fault modelling and testing,

synthesis of quantum comput ers, and graph algorithms.

She

dis cussed

many

physical

limitat ions in VLSI like overheat ing or power

usage, strict er des ign ru les and th e t echn iques used to ove rcome these limitations lin e.

Statistical Inst itute, Kolkata

On the second day Dr. Mandar Mit ra spoke on

Information Ret r ieval (IR). IR addresses the problem of

f ind ing

useful inf ormat ion

in

response to a userâ&#x20AC;&#x2122;s query or informat ion need. Automated information ret rieval systems are used to redu ce what has been called

information overload. Many universit ies and public lib raries use IR systems to provide access

to

books,

journa ls

and

other

documents. Web s earch engines are poss ibly the most familiar examples of IR systems. He discussed On day one Dr. Bharghab Bhattacharya, the much await ed sp eaker of the event grabb ed the crowdâ&#x20AC;&#x2122;s attention by his talks. He spoke on recent

advances

in

Microf luid ics

Dept. Of CSE, Heritage Institute of Technology

some

of

the

as

well

basic

models

and

as

methods

for

techniques used in I R (such as the Vector Space

Mode l),

evaluat ing the eff ect iveness of these mod els and techniques.

and

Page 19

Dr.

Subhas

Chandra

Nandy

was

the

last

speaker of th e event. He discussed one of t he important

areas

Optimization pract ical

of

computer

Prob lems.

geomet ric

There

science

are

opt imizat ion

and disk graphs, maximu m clique prob lem of rectangle int ersect ion graphs and d isk graphs

â&#x20AC;&#x201C;

many

problems

which are computationally hard. Some of t he standard paradig ms

for

desig ning

approximat ion alg orithm for those problems were

d iscussed.

demonstrated

by

Some him

of

are

th e

the art

problems gallery

opt imization problems, maximum independent set p roblems for r ectangle inte rsection graphs

Dept. Of CSE, Heritage Institute of Technology

Page 20

List of Publications by faculty and

students

of



Joydeep Das, Subhashis Majumder, and Prosenjit Gupta, Voronoi Based Location

CSE

Aware Collaborative Filt ering, pp. 179-

Department of HIT [January to

183, 3rd IEEE National Confer ence on

June 2012].

Emerging Trends and Applicat ions in Computer

Science(NCET ACS),

March

2012. 

Arpan

Chowdhury,

Basuchaudhuri,

Partha

and



Srinathan,

Subhashis

Agarwal,

Majumder, Spread of Informat ion in a

Points

Socia l Network us ing Influent ial Nodes,

Lecture

Not es

in

Biswajit Sanyal, Prosenjit Gupta, and Subhashis

Majumder,

Top-K

Range-

Agg regate Qu eries on Categorical Data, pp.

143-147,

3rd

IEEE

National

Conferen ce on Emerging Trends and App lications

in

Computer

Science(NCETACS), March 2012.

Dept. Of CSE, Heritage Institute of Technology

Page 21

Ag gregate

in

the

Plane, 6th

J.

Maximal

pp.

52—63,

Workshop

on

Computer Science, Vol. 7157, February

Science,

2012.

7302, Spr inger, May 2012. 

Range

and

2012, Springer Verlag Lecture Notes on

PAKDD(2),

C omputer

Kot hapalli,

Algorith ms and Computation, WALCOM

Discovery and Data Mining - 16th Conference,

K.

Proceed ings,

pp. 121-132, Advances in Knowledge Pacif ic-As ia

A. S. Das, P. Gupta, A. K. Kalavagattu, K.



Hardware Acceleration using M itr ion- C Satarupa

Guha,

J.

M.

Manasa,

and

Trisha Nandy, presented at All Ind ia Inter

Eng ineering

College

Academic

Meet, organized by Forum of Scient ists, Eng ineers 2012.

and

Technologists,

March

A Simple USB Device Driver on

with d river (more on this late r). The “.p robe”

Linux platforms

and “.disconnect” f ields refer to the funct ions

B y P ro f . A rin d am C h at te rjee , A s s i st an t

unloading respect ively. The USB driver is then

to be called dur ing dr iver modu le loading and

P ro f e s so r, CS E

regist ered with a call to usb_ reg ist er, in t he

Introduction:

driver’s in it function, as shown here

For the last decade or so, USB devices are

static int __init usb_first_init(void) { int result; /* register this driver with the USB subsystem */ result = usb_register(&first_driver); if (result < 0) { err("usb_register failed for the "__FILE__ "driver." ,"Error number %d", result); return -1; } return 0; } module_init(usb_first_init);

ruling the world of comput er I/O devices. Be it ca mera, prin ter, pen drive or net connector devices, USB devices are omn ipr esent now. But many

of

these

devices

cannot

function

properly , especially with the Linux platforms, wher e even simple d evice drivers for these USB devices may not exist. Th is art icle is aimed at beg inn ers in Linux pr ogra mming and sys admins who want to boost their power over Linux p latforms by understanding h ow to write s imple USB device drivers on L inux.

R egist ration The first thing a Linux USB driver needs to do is reg iste r itself with the Linux USB subsystem (part of Linux kernel). This part (of the

D eregist ration: usb_unreg ist er funct ion: static void __exit usb_first_exit(void) { /* deregister this driver with the USB subsystem */ usb_deregister(&first_driver); } module_exit(usb_first_exit);

driver) is resp onsible for provid in g the OS

Please not e the use of the usb_dr iver st ructu re

with

(here named as “first_ driver”) in the ca lls to

some informat ion about which devices

the dr ive r supports; what are the funct ion s to call when a support ed device is inserted or removed fr om the system etc.

usb_reg ist er and usb_dereg ister funct ions.

USB Device Ope rations: After registering a USB device driver with t he

static struct usb_driver first_driver = { .name = “firstusb”, .probe = first_probe, .disconnect = first_disconnet, .fops = &first_fops, .minor = USB_FIRST_MINOR_BASE, .id_table = first_table,};

OS, the ne xt task the driver undertakes is to prepare the device to be used by the OS for further

“.name” f ield gives a name to this driver module;

op erat ions.

Immed iate ly

b elow

we

descr ibe th e initia lization which should t ake place once the device is regist ered. Then we immed iately dea l with the case when the

A set of file operations (“.fops”) funct ion

device will be d iscon nected / r emoved

point ers

the system

enable this user-space interaction

Dept. Of CSE, Heritage Institute of Technology

Page 22

fr om

During registration:

The cor respond ing fu nct ion prot otypes are declared as shown below :

static int first_probe(struct usb_interface *interface, const struct usb_device_id *id)

The dr iver now needs to ve rify that this device is actually one that it can accept. If so, it returns 0. If not,

or if any error occurs durin g init ialization, an er rorcod e (such as -ENOMEM or -ENODEV) is returned f rom

static int first_open(struct inode *, struct file *); static int first_release(struct inode *, struct file *); static ssize_t first_read(struct file *, char *, size_t, loff_t *); static ssize_t first_write(struct file *, const char *, size_t, loff_t *);

Open: The first_open f unct ion w ill be ca lled from a user program t rying to ta lk t o the device. The first funct ion called w ill be open,

the probe funct ion. [Her e also not e the use of

as the p rog ram tries t o op en th e device for

the cor respond ing funct ion d ef ined in the

I/O. A code exa mple is g iven below:

“.prob e”

field of

the usb_dr iver

struct ure

def ined at the top.]

During d isconnect: When the device is removed from the USB bus, the dis connect funct ion ( as declared in t he “.disconne ct” f ield in the usb_dr iver structu re)

static int first_open(struct inode *inode, struct file *file) { /* increment our usage count for the module */ ++first->open_count; /* save our object in the file’s private structure */ file->private_data = dev;

} b) After the open fun ction is called, the

is called with the d evice pointer. The driver

read and writ e fun ct ions are ca lled to

needs to clean any private data that has been

receive and send data to the device. But

allocated at this t ime. The driver unregist ers

before we g o to the d etails of the read

itself from the devfs subsystem with the devfs_unreg ister call.

and write funct ions, let us look into an

Other device op erations:

re levant in USB context .

important

The fou r most import ant operations the d evice needs to support are : open , close (called “release” here) , read and write. The follow ing

con cept

called

URB

very

USB urbs: [ I am more or less copying f rom Resource # 8]

is a def in ition of th e file op erat ions st ructure

=> 'What is an URB?'

(to be included in the .fops field in t he

The bas ic idea of th e new d river is message

usb_dr iver structure):

passing, the message itself is called USB Request Block, or URB for short.

struct file_operations first_fops = { .read = first_read, .write = first_write, .open = first_open, .release = first_release };

=> The URB st ructure Some of the fie lds in an URB are: struct urb

Dept. Of CSE, Heritage Institute of Technology

Page 23

It does everything usb_unlink_ur b does, and

{ // (IN) device and pipe specify the endpoint queue struct usb_device *dev; // pointer to associated USB device unsigned int pipe; // endpoint information unsigned int transfer_flags; // ISO_ASAP, SHORT_NOT_OK, etc. // (IN) all urbs need completion routines void *context; // context for completion routine void (*complete)(struct urb *); // pointer to completion routine // (OUT) status after each completion

in addition it waits until after the URB has been returned and the comp let ion handler has finished.

Thus you can be sure that when

usb_kill_urb() returns, the URB is t otally idle. => What about the comp let ion handler?

The hand ler is of the following type typedef void (*usb_complete_t)(struct urb *,

// (IN) buffer used for data transfers : : : // (OUT) sometimes only part of CTRL/BULK/INTR transfer_buffer is used : : : // Only for PERIODIC transfers (ISO, INTERRUPT) // (IN/OUT) start_frame is set unless ISO_ASAP isn't set : : :

struct pt_regs *) i.e., it gets the URB that caused the complet ion call, p lus the reg ist er values at the time of t he correspond ing int er rupt (if any). Since the context para met er is included in the URB, you can

// ISO only: packets are only "best effort"; each can have errors : : : < parts deleted for simplicity > };

pass

handler.

informat ion Now

we

are

to in

the a

complet ion position

to

understand the w rit e f unct ion in detail:

=> How t o sub mit an URB?

In the first_w rite f unct ion, we rece ive a

Just call

send to the

point er to some data that the user wants to

int usb_sub mit_urb(struct urb

*urb, int mem_flags)

device and the size of the data

=> How t o cancel an already runnin g URB?

Write

There are t wo ways to cancel an URB you've

static ssize_t first_write(strucfile *filp, const char *buffer,

submitted but wh ich hasn't been retu rned to

size_t len,

your d river yet.

For an asynchronous cancel, ca ll

loff_t *off) {

/* we can only write as much as 1 urb will hold */ bytes_written = (count > first->bulk_out_size) ? first->bulk_out_size : count;

int

usb_unlink _urb(struct urb *u rb).

/* copy the data from user space into our urb */

It removes the urb f rom the int erna l list and

copy_from_user(first->write_urb>transfer_buffer, buffer, bytes_written);

fre es all a llocated HW descriptors. Note that the URB will not normally have fin ished w hen

/* set up our urb */

usb_unlink _urb() returns; you must still wait

usb_fill_bulk_urb(first->write_urb,first->dev, usb_sndbulkpipe(first->dev, first>bulk_out_endpointAddr),

for the comp let ion handler to b e called.

To cancel an URB synchronous ly, call usb_kill_urb(struct ur b *urb)

Dept. Of CSE, Heritage Institute of Technology

void

first->write_urb->transfer_buffer, bytes_written, first_write_bulk_callback, first); /* send the data out the bulk port */

Page 24

Hotplug:

result = usb_submit_urb(first->write_urb); if (result) {

To enable the linux- hotplug system to load

err("Failed submitting write urb, error %d", result);

the driver automatically when the device is plug ged in, you

} }

When the wr ite urb is f illed up with t he proper

infor mation

using

t he

usb_fill_bulk_urb funct ion, we

need to create a MODULE_DEVICE_TABLE. T he following code t ells the hotp lug scr ipts t hat this

point th e urb’s completion ca llback to call our own f irst_w rite_bulk_ callback funct ion

module

supports

a

single

device

w it h

a

specif ic vendor and pr oduct I D: /* table of devices that work with this driver */

R ead: The read funct ion works a bit diff erent ly from

static struct usb_device_id first_table [] = {

the wr ite funct ion in that we do not use an

{ USB_DEVICE(USB_FIRST_VENDOR_ID, USB_FIRST_PRODUCT_ID) },

urb t o t ransfer

{ } /* Terminating entry */

data from the device t o the dr iver. Instead we

};

call the usb_bulk _msg function, which can be

MODULE_DEVICE_TABLE (usb, first_table);

used to send or receive data from a device without havin g to create urbs and handle urb

Background: In

comp let ion callback f unctions.

Heritage

projects

static ssize_t first_read(struct file *filp, char *buffer, /* The buffer to fill with data */ size_t length, /* The length of the buffer */ loff_t *offset) /* Our offset in the file */

Inst itut e

were

department

of

Technology,

undertaken

regarding

USB

in

th e

device

t wo CSE

dr ivers

during th e 2011 – ’12 season. One project was on writ ing a USB based Print er Driver for

{ /* do an immediate bulk read to get data from the device */

a HP pr int er for which no known dr iver ex ists

retval = usb_bulk_msg (first->dev,

on Linux platforms. Another was a USB based traffic light simulator. Many more projects

usb_rcvbulkpipe (first->dev,first>bulk_in_endpointAddr),

based on USB / L inux are in the pip eline.

first->bulk_in_buffer, first->bulk_in_size, &count, HZ*10);

Conclusion:

/* if the read was successful, copy the data to user space */

In this art icle an attempt has been made to

if (!retval) {

show the basics of writing a simp le USB

if (copy_to_user >bulk_in_buffer, count))

(buffer,

first-

retval = -EFAULT; else retval = count; }}

device dr iver on Linux. This code cannot be comp iled and used as it is – but a working prototype can be bu ilt ve ry easily from t his code.

Also

transfer

Dept. Of CSE, Heritage Institute of Technology

Page 25

–

this

su pports

neither

only

int er rupt

bulk

d ata

dr iven

nor

isochron ous data. But once again these can be

*Prog ramming Guide for Linux USB Device

done very easily by mod ifying this code.

Drivers: http://usb.cs.tum.edu/usbdoc *USB Home Page: http://www.usb.org; USB on

Resources

Wik ipedia: http://en.wik ipedia.org/wik i/USB

*Writing USB Device Drivers: Greg Kroah-

*Linux

Hartman

http://www.mjmwired.net/kernel/Docu mentati

*The Linux USB Project: http://www.lin uxusb.org/ (http://www. linux-usb.org) *Linux

Hotplug

Project:

(http://linux-

hotplu g.sourceforge.n et) *Linux

USB

Working

Devices

on/usb/URB.txt;

*Writ ing

for a

USB

Linux

:

Kerne l

Driver for an Unknown USB Device: Matthias

List:

*Character Device D rivers (from the Linux Kernel Module Progra mming Guid e) : http://tldp.org/LDP/ lk mpg/2.4/html/ c577.ht m

http://www.qbik. ch/usb/devices/ (http://www.qbik.ch/usb/devices )

Dept. Of CSE, Heritage Institute of Technology

doc

Vallent in

http:// linux-

hotplu g.sourceforge.n et/

Kernel

Page 26

Fault-Tolerant Systems

cause transient failu res by perturbing t he

S y n o p s i s b y M r. Kau s ta v C ho u d hu ry, 1 s t

damage to the hard ware system. Messages

system state without causing any permanent

Y ea r, M Te c h, CSE

The

following

““Dist ribut ed

is

propagating from one process to another may a

Systems

synopsis and

of

the

Networ ks”

workshop conduct ed by Prof. Sukumar Ghosh, Prof essor,

Depart ment

of

Comp uter

Science, Univers ity of Iowa, USA and

Prof.

Somprakash

be lost in transit. F inally, even if hardware

does not fail, s oftwar e may fail due to code corrupt ion, system intrus ions, imp roper or

unexpected changes in the specif icat ions of the system, or environ menta l changes.

Failu res are a part of any system — the real issue is the f requency of the failures and the ir

Bandyopadhyay, Professor, Management Infor mation System group, IIM, Kolkata held on 22.03.2012

consequences.

The

comput er

system

ENIAC had a mean time between fa ilu res (MTBF) of five minut es. The rea l inte rest on

dependable comput in g started f rom the t ime of space exp lorat ion , where the cost of a

ABSTRACT:-

A fault is the manifestation of an unexpected behavior, and fault-tolerance is a mechanis m that masks or restores the expected behavior of a system follow ing the occu rrence of faults.

Attention to fault-tolerance or dependability has drastically increased over recent years due to our increased dependence on computers to perform critical as well as noncritical tasks. Also, the increase in the scale of such systems indirectly contributes to the ris ing number of faults. Advances in hardware engineering can make the individual components more dependable, but it cannot eliminate faults altogether. Bad system des igns can a ls o contribute to failures.

failur e is unacceptab ly high. The w idesp read

use of computers in the financial world as we ll

as

reactors,

in

crit ical

systems

lik e

nuclear

air-t raffic

control

or

patient

monitoring systems where human lives are direct ly affected, have ren ewed interest in t he study of fault-tolerance.

2. CL ASSIFI CATION OF FAULTS:The major classes of f ailur es ar e as follows: Crash failure:-

A

process

und erg oes

cr ash

failur e, when it permanently ceases to execute its act ions. This is an ir revers ible change.

Ther e are severa l variat ions in this class. In

1. INTRODUCTION:-

one variat ion, crash failures ar e t reated as reversib le, that is, a process may play dead for

Histor ically, models of failu res have been

a finit e period of time, and then resume

specificat ion of a system. A VLSI design er may

are

wher e

are

detect ed w ith t otal ce rtainty, s ince th ere is no

regardless of input variat ions. A dip in t he

can execut e its act ions. In a synchronous

link ed with the level of abstract ion in the focus on stuck-at-0 and stuck-at-1 faults the

outputs

of

certain

gates

permanent ly stuck to either a 0 or a 1, power supply voltage or radio interferences

due to a lightning, or a cosmic shower can

Dept. Of CSE, Heritage Institute of Technology

operat ion, or it may be repaired. Such fa ilu res called

napping

failur e.

In

an

asynchronous mod el, crash failures cannot be lower bound of the s peed at which a process system where processor speeds and channe l delays are bounded, crash failure can be

Page 27

detect ed using t imeout. When other corr ect

processes fail t o receive the heartbeat s ignal within a predef ined timeout period, they conclude that the process has crashed.

sendin g a sequence of messages to a receiver process. If the receiver does not receive one or more of the messages sent by the transmitt er,

then an omission failure occurs. In real life, be caused

in IBM’s DB2 production code are supposedly nondete rminist ic

in

nature

and

are

t hus

transient. Gray and Reuter est imated in 19 93

Omission failure:- Consider a t ransmitter p rocess

this can

testing phase. For instance, over 99% of b ugs

either

by

transmitter

that there are 2 t o 3 bugs every 1000 lin es of code.

Byzantine

failur e:-

Byzantine

failu res

represent the weakest of all the failure mod els that

allows

every

conceivable

for m

of

malfunct ion, or due to the prop ert ies of the

er roneous behavior. As a specif ic example,

medium. For examp le, limit ed buffer capacity

assume that process i forwards the valu e of a

in the routers can cause some commun ication systems

to

drop

communication,

packets.

mes sages

In

are

wir eless

lost

when

collis ions occu r in the MAC layer, or the receiving n ode moves out of range.

local variab le to each of its neighbors. Then the followin g are examples of inconsist ent behaviors: • Two d ist inct neighbors j and k receive values

Transient failure:- A transient fa ilu re can pert urb

x and y, where x != y.

the state of processes in an arb itrary way. The

• Every ne ighbor receives a valu e z where z !=

agent

x.

indu cing

t his

fa ilure

may

be

momentarily act ive (lik e a power surge, or a me chanical shock, or a lightning), but it can make a last ing effect on the globa l state. In

• One or mor e neigh bors do not receive any data from process i.

fact, omission failu res are specia l cases of

Some poss ible causes of the above kind of

transient failures, when the channel states are

byzantine failu res are (1) Total or par tia l

pertu rbed. Transient faults can occur due to

breakdown of a link joining i with on e of its

effects gamma

of

environmental hazards

rays,

whose

duration

in

such

as

neighbors, (2) Software p rob lems in process i,

t ime

is

(3)

Hardware

synchronizat ion

p rob lems—

limited. Transient failures are also caused by

assume that every neighbor is conn ect ed to

an overloaded power supply or weak batteries.

the same bus, and reading the same copy sent

Hardware faults ar e not the only sour ce of

out by i, but since the clocks are not perf ectly

transient faults. T ransient failu res can result

synchronized, they may not read the value of

due to state corruption that occurs when

x exact ly at the same t ime. If th e va lue of x

software components fail. Gray called th em

varies with time, then different n eighbors of I

Heisenbugs , a class of temporary internal

may rece ive different values of x from process

faults that is intermit tent in nature. They are

i. (4) Malicious act ions by pr ocess i.

essent ially permanent faults whose cond it ions of activat ion occur rarely or are not easily reproducible, and so diff icult to d etect in t he Dept. Of CSE, Heritage Institute of Technology

Software failure:- There are several primary reasons that lead to software failure:

Page 28

(1) Coding errors or human errors: As an

year 2000 dawned. The prob lem was with

examp le, on Sept ember 23, 1999, NASA lost

inadequate

the

spacecraft

were wr itten in th e 20th centu ry for f inancial

because one engin eering t eam used metr ic

inst itut ions, power p lants or process contr ol

units

systems, the year 19xy was most often cod ed

$125

million

while

Mars

another

orbiter

used

Eng lish

units,

leading to a navigat ion f iasco, causing it to burn in the atmosphere.

landed

f lawlessly

on

the

Mart ial

surface on July 4, 1997. Howeve r, later its communication failed due to a des ign flaw in the

real-t ime

wh en

progra ms

as xy, so 1999 wou ld appear as 99.

Security failure:-

(2) Software des ign errors: Mars pathfinder mission

specif ica tions:

embedded

software

k ernel

VxWorks. The prob lem was later diagnosed to be caused du e to priority inversion, when a medium p riority task could preempt a high

Virus and other kinds of malicious software creeping into a computer system can lead to unexpected

behaviors

that

manif est

themselves as fault. Various kinds of intrusion lead

to

failures

eavesdropping

or

â&#x20AC;&#x201D;

these

stealing

of

include passwords,

leading to a compromised system.

priority on e.

Some failu res ar e repeatable, wh ereas

(3) Memory leaks: The execut ion of prog rams suffers from th e deg enerat ion of the run-t ime system due to memory leaks, leading t o a system crash.

others are not. Failu res caused by incorr ect software are oft en repeatable, whereas those due to transient hardware ma lfunct ions or due to race cond it ions may not be so and therefore not det ect ed dur ing debu gg ing. In

of

the doma in of software failur es, Heisenb ugs

specificat ion: Assume that a system runn ing

are diff icult to detect. Finally, human errors

prog ram S is producing the int ended results.

play a big role in system failure. In November

If the system suddenly fails to do so even if

1988, much of th e long-distance service along

there is no hardware failur e or memory leak,

the

then

construct ion

(4)

Prob lem

there

with

may

the

be

inadequacy

a

problem

with

East

Coast

was

crew

disrupted

accidentally

when

a

sever ed

a

specificat ions. If {P}S{Q} is a theore m in

major f iber opt ic cable in New Jers ey; as a

prog ramming log ic, and the precondit ion P is

result, 3,500,000 call attempts were b locked.

inadvertent ly weakened or a ltered, then ther e

On Sept ember 17, 1991 AT&T technicians in

is no guarantee that the postcond it ion Q w ill

New York attend ing a seminar on warning

always hold !

systems failed to respond to an activated alarm for s ix hours. The resu lt ing p ower

The Y2K Prob lem:-

failur e b lock ed n early 5 million domest ic and

A classic example of software failure is the

internat ional ca lls, and paralyzed a ir t rave l

so-called Y2K bug that rocked the wor ld and

throughout

kept

1,170 flights to be canceled or delayed.

millions

of

service

providers

in

an

uneasy suspense for several months as the Dept. Of CSE, Heritage Institute of Technology

Page 29

the

Nor theast,

causing

near ly

applicat ions where t he failur e can endanger

3. FAULT-TOLERANT SYST EMS:We designate a system that does not tolerate failures as a fault-in tolerant system. In s uch systems, the occurr ence of a fault violates some liven ess or safet y property. Let P b e t he set of configu rations for the fault- intoler ant system. Given a set of fault act ions F, the fault span Q corresponds to the lar gest set of configurat ions that the system can get into. It is a measure of how bad the system can become. The following two condit ions are tr ivially true:

human lif e or cause massive loss of property.

An aircraft must be able to f ly even if one of its eng ines ma lfunct ions. A patient monitoring system in a hospital must not r ecord pat ient data incorrectly even if some of the sensors or inst ruments

malfun ction,

potent ially

cause

an

since

this

improper

dose

can of

med icine to be ad ministered to the pat ient and endanger

her/his

life.

Masking

tolerance

preserves both liveness and safety propert ies of the or igina l system.

Nonmasking t olerance:- In nonmasking fault-

1. P ! Q.

tolerance, faults may temp orarily affect t he

2. Q is closed under t he actions of both S and

applicat ion and violate the safety property,

F.

t hat i s, P !

A system is called F-tolerant (i.e., faulttolerant with respect to the fault act ions F), when

the

system

returns

to

its

or iginal

configurat ion ( i.e., P holds) after a ll F-actions stop execut ing. There are four major types of fault-tolerance:

for rout ing table computation broke the cycle

that

packets

eventually

reached

t he

are

things

eventually

happen.

Masking tolerance:- When a fault F is masked, has

d ifferent In of

types

backward the

system

of

nonmasking

er ror are

recovery, period ically

recorded on an incorrupt ible form of storage,

g ood

no

impact

on

t he

applicat ion, that is, P = Q. Masking tolerance in

the

snapshots

things never happen. The essence of a liven ess

important

trap a few packets. However the algor ithms

tolerance.

A safety property int uit ively imp lies that bad

is

failur e create a cyclic path in the rout es, and

Ther e

• Graceful degradation

occurrence

from a source to a dest ination nod e. Let a

an increase in the message propagation delay.

• Fa il-safe tolerance

its

is restored. Cons ider the r out ing of pack ets

dest ination. The net impact of the failu re was

• Nonmask ing tolerance

is

compromised, and eventually normal behavior

and

• Masking tolerance

property

Q. How ever , l i veness i s not

many

Dept. Of CSE, Heritage Institute of Technology

safety-critical

called

stable

storage.

When

a

failure

is

detect ed, the system rolls back to the last conf igurat ion saved on the stable storage ( to undo the effect

of

the failu re), and the

computation progresses from that point. In forward error recovery, when a fault occurs, the system does not look back or t ry a rerun, since

minor

in consequent ia l,

Page 30

g lit ches as

long

are as

cons idered the

normal

operat ion recovery

is

restored.

Forward

mod ify files, but can on ly read the f iles t hat

guarantee

recove ry

already exist. One can also argue that it is a

eventually

systems

that

from an arbitrary initia l state are kn own as self-stabilizing systems.

Fail-safe

t olerance:-

fail-safe system.

References:-

A

fail-safe

system

relaxes the t olerance requirement by only avoid ing those fau lty configurat ions that may have catastrophic consequences, even when

[1] Sukumar Ghosh, Dist r ibut ed Systems - An Algorith mic Approach , 2006 CRC Press (ISBN 158488564).

failures occur. Given a safety specif icat ion P,

The material dis cussed is an abridg ed version

a fail-safe system preserves P desp ite t he

of [1]. Pr of. Suku mar Ghosh is a visit ing

occu rrence of failures. However, there is no

faculty at Her itage Institut e of Technology

guarantee that liven ess will be preserved.

and

Somet imes, halt ing p rog ress and leaving the

Dist ributed Comput ing. For more d etails log

system in a safe state may be the best possible

on to, http://www.d ivms.uiowa.edu/~ghosh/.

teaches

a

one-semester

course

on

way to cope w ith failures. The ground cont rol system of the Ariane 5 launcher was desig ned to mask all sing le faults, but when two

Related W orks:-

successive component failures occur, it would

[1] Arora, A. and Ku lkarni, S.S., Component

postpone the launch (this is safer than a

based design of mu ltit ole rance, IEEE T rans.

mishap in the space).

Software Eng ineering, 24 (1), 63–78 (January

Graceful degradation:- There are systems that

1998).

neither mask, nor fu lly recover f rom the eff ect

[2] Arora, A. and Gouda, M.G., Closur e and

of failu res, but exh ibit a degraded behavior

convergence: A f oundation of fault-tolerant

that falls short of the nor mal b ehavior, but is

comput ing. IEEE T rans. Software Eng., 19(11),

still cons idered acceptable. The notion of

1015–1027 (1993).

acceptability

is

hig hly

subject ive,

and

is

ent irely dependent on the user runn ing the applicat ion.

Some

examples

of

deg raded

behavior are as follows: Wh ile routing a message between two points in a networ k, a prog ram computes the shortest path. In the

[3] Ezh ilchelvan, P.D . and Srivastava, S., A characterization of Symposium

on

faults in systems.

Reliability

in

5th

D istr ibut ed

Software and Database Systems, pp. 215–2 22 (1986).

presence of a failure, if this progra m returns

[4]

another path which is not the shortest path

tolerant

but one that is margina lly longer than the

asynchronous environ ments. A CM Comput ing

shortest one, then this may be considered

Surveys, 31(1), 1–26 (1999).

acceptable. An operating system may switch to a safe mode when users cannot create or

Dept. Of CSE, Heritage Institute of Technology

Page 31

Gaertner,

F.C.,

Fundamenta ls

distribut ed

of

fault

comput ing

in

Telnet over SSL with Z-modem

prog ram t o machine specif ic language fr om

B y M r. So um abh o Ba n e rje e , 4 t h Ye a r,

termina l, so that it looks as if the input is

NVT and submits the program to a pseud o-

B Tec h , CSE

given by the user on the same comput er. Then

the computation is carried out and result is

Introduction: The

sent to the oth er s id e follow ing same pattern.

purp ose

of

this

project

t elnet

and

SSL

is

to

provid e secure information exchange usin g a comb ination

of

prot ocols

betwe en two systems. For file ex change in

bulk, Zmodem f ile t ransfer prot ocol has also been integ rated into t he softwar e.

Now a day when the cost of technology is much reduced, this protocol is used for d ata

transfer on ly. t elnet uses several command asDO,DONâ&#x20AC;&#x2122;T,WILL,WONT

and

severa l

sub

opt ions to negot iate the types of ter minal,

speed of data, and other opt ions w ith t he

Vital components:-

other side. But there is a prob lem with t his

a) T elnet:-

type

Telnet is

too. Telnet as such does not take care of any

a net wor k

protocol used

on

the Inter net or local area networ ks to provide a

bid irect ional

in teract ive

communications

facility

virtua l terminal connect ion. int erspersed

in with

text-or iented using

User

a

data

Telnet

is

cont rol

infor mation in an 8-bit byte orie nted d ata connect ion

over

th e Transmission

Control

Pr otocol (T CP).

As in the past times comput er mach ines were qu iet cost ly, there wer e one cent ral mach ine with a pr ocessor and there was several terminals wit h a monitor and a key

board forming a ter mina l through wh ich the end users connected the central server to users

had

the

prog rams

and

The

(network

Sock ets

Layer

usually

over T CP and is short to say, SSL is r ecogn ized as the bottom line in security, which stands for

secu ring th e communicat ions b etween

servers-to-client and server-to-server, load balancin g devices. Th e protocol is compos ed of two layers. ď&#x201A;ˇ

they

virtual

ter mina l) character set, common standard for

transmission, and sen ds it through the link to the centra l server. On the other sid e w hen

telnet receives the prog ram it t ranslates the

Dept. Of CSE, Heritage Institute of Technology

Secu re

capable of secu ring any protocol that works

to it. When the te lnet receives the program it NVT

D ata

abbreviated as SSL is an excellent prot ocol

the telnet for the result and hand the progr am a

and

b) Secured Socket Layer(SSL):-

the reviva l of the program th e ter mina l asked

to

Integ rity,

Signat ure,

any file transfer.

prog ram will run in the ir own machine. On

it

Data

Elect ronic

Confid ent iality. Moreover it cannot handle

submitted the m to t he terminal as if t he

converts

secur ity,

Authent ication,

carry out their computational works. Here t he end

of

Page 32

SSL Handshake Prot ocol a llows the server

and client t o authent icate each other and to negot iate an en cryption a lgorith m and cryptographic k eys before the application

protocol transmits or receives its f irst byte of data.

SSL Record Protocol is layered on top of

ď&#x201A;ˇ

some

re liab le

transport

prot ocol

(e.g.,

TCP). The SSL Recor d Protocol is used for encapsulat ion

of

various

higher- level

protocols.

When an SSL client in it ially connects to an SSL server, th ey perfor m a handshake to

establish security attr ibutes and exchange cert ificates as shown in the figu re1.

SSL is a layered prot ocol. At each layer, messages

may

include

fie lds

for

length,

description, and cont ent. SSL takes messages

to be transmitt ed, fragments the data into

manageable blocks, optionally comp resses the

cons ist of a header followed by 1 or more d ata sub packets. In the absence of t ransmission er rors, an entire f ile can be sent in on e d ata frame. With equiva lent binary (efficient) and hex (applicat ion f riendly) frames, the sending prog ram can send an "invitat ion to rece ive " sequence to act ivate the receiver without crashing

the

re mote

applicat ion

with

unexpected cont rol characters. Frames begin with a header wh ich may be 16bit CRC b inary, 16bit CR C hex or 32 b it binary. A typical ZMODEM sending

session program

starts w ith

with the

ca lling

names

of

t he the

desir ed file(s) and opt ion(s). The sending prog ram may send the str ing "rz\ r" to invoke the

receiving

p rog ram

from

a

poss ible

command mode. Th e "rz" followed by carr iage retu rn act ivates a ZMODEM receive program

data, applies a MAC, encrypts, and transmits

or command if it were not already active. The

the

sender may then display a message intended

resu lt.

Received

data

is

decrypted,

ver ified, decompressed, and reassemb led, t hen delivered to higher level clients. Thus it has following

advantages

Authent ication,

Elect ron ic

Data

Signature,

Integrity,

Conf ident iality etc.

Data 1.

provides

a

general

purpos e

cases, the file lengt h may be unknown, as data

Int eg ration:-

it canâ&#x20AC;&#x2122;t send any files as a whole and the lack

applicat ion to file transfer protocol. In some when

requ ested, etc.

One of th e basic problems of th e telnet is t hat

c) Z-modem:Zmode m

for human consumpt ion, as a list of th e f iles

is

obtain ed

from

a

of security. On the other hand SSL is being used quiet successfully with other protocols which were lacking security e.g. HTTP to secure the underlying data

process.

Var iable length data sub packets used in ZMODEM solves this prob lem. In ZMODEM, the length of data sub packets is denoted by end ing

each

sub

packet

w ith

an

escape

sequence s imilar to BISYNC and HDLC. The end result is a ZMODEM header containing a "f rame

type",

fou r

bytes

of

supervis ory

infor mation, and its own CRC. Data frames

Dept. Of CSE, Heritage Institute of Technology

Page 33

exchange & zmodem can be used for the file transfer.

done by a pipe or a file where zmodem writes and telnet

We here had used the OpenSSL crypto libraryâ&#x20AC;&#x2122;s APIs to

reads from. When telnet receives anything it sends it

create a upper layer SSL read write functions and

through the underlying security of SSL and then

replaced the send() and recv() functions of telnet to

through TCP/IP stack to other side where the data is

integrate them and form telnet-SSL. Then integrate

received by SSL and handed over to telnet. Then telnet

zmodem with it so that whenever a user asks it to file

delivers the data to the zmodem which writes them in a

transfer, zmodem takes it, breaks it into parts and asks

file and on completion informs the users that the data

the telnet program to transfer it. This integration can be

transfer is complete.

Dept. Of CSE, Heritage Institute of Technology

Page 34

CROSSWORD

ACROSS 3. The __ diagram is used to depict in what order and how processes A

and B operate with one another.

4. Process A and Process B both want resource R.

What should be used to control access?

5. Here nothing is exact,

what is important is the degree of truthfulness

1. This is a kind of selection control technique used in C 2. Itâ&#x20AC;&#x2122;s a technique to reduce dependency and redundancy in DBMS. DOWN 1. This is a java programming language class. As the name implies, it serves a client request and receives a response from the server

2. ___ is a technique in computer architecture that allows subsequent instructions to be fetched while the processor performs operations, queue them in a buffer until the time when the instruction operation can be performed.

3. These are used in browsers to remember the user activities or the state of the website.

4. This is a network flow control mechanism with a funny name that reminds one of a common house hold item!

5. This is one of the most primitive software engineering models with a name that reminds one of hill stations and valleys

Solution will be published in the next issue. However, if you donâ&#x20AC;&#x2122;t want to wait till then, you can also mail me your answers @ reshma.roychoudhuri@heritageit.edu .

Also, you are requested to contribute for this magazine. Please mail your contributions and also queries, suggestions and letters to the editor to the above mentioned email id

Dept. Of CSE, Heritage Institute of Technology

Page 35