Operating
Systems
RSA
ALGORITHM
Study and implementation
of RSA Algorithm using C programming
language.
In a classic cryptosystem in
order to make sure that nobody,
except the intended recipient,
deciphers the message, the people
involved had to strive to keep
the key secret. In a public-key
cryptosystem. The public key
cryptography solves one of the
most vexing problems of all
prior cryptography: the necessity
of establishing a secure channel
for the exchange of the key.
RSA algorithm is a public-key
cryptosystem defined by
Rivest, Shamir, and
Adleman. The
scheme is as follows:
Let p and q be distinct large
primes and let n be their product.
Assume that we also computed
two integers, d (for decryption)
and e (for encryption) such
that
d * e 1 (mod ø(n))
where ø(n) is the number
of positive integers smaller
than n that have no factor except
1 in common with n
The integers n and e are made
public, while p, q, and d are
kept secret.
Let m be the message to be
sent, where m is a positive
integer less than and relatively
prime to n. A plaintext message
is easily converted to a number
by using either the alphabet
position of each letter (a=01,
b=02, ..., z=26) or using the
standard ASCII table. If necessary
(so that m<n), the message
can be broken into several blocks.
The encoder computes and sends
the number
m' = m^e mod n
To decode, we simply compute
e^d mod n
Now, since both n and e are
public, the question arises:
can we compute from them d?
The answer: it is possible,
if n is factored into prime
numbers.
The security of RSA depends
on the fact that it takes an
impractical amount of time to
factor large numbers.
RSA ALGORITHM
RSA MD5Source
Code(rsa algorithm in Visual
C++ source code)
RSA Algorithm
program in JAVA (RSA Signature
and Calculations) by
Orlin from his java cryptography
page
RSA Algorithm
Implementation in C language
The Cigarette-Smokers
Problem.
The Cigarette-smokers problem:
Consider a system with three
smoker processes and one agent
process. Each smoker continuously
rolls a cigarette and then smokes
it. But to roll and cigarette
and then smokes it. But to roll
and smoke a cigarette, the smoker
needs three ingredients: tobacco,
paper and matches. One of the
smoker processes has an infinite
supply of all the three materials.
The agent places two of the
ingredients on the table. The
smoker who has the remaining
ingredient then makes the smokes
a cigarette, signaling the agent
on completion. The agent then
puts out another two of the
three ingredients, and the cycle
repeats. Write a program to
synchronize the agent and the
smokers.
