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December 9, 2011 21:41
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Number Theory & Cryptography - Assignement 2 - Question 3: Implement RSA Cryptosystem. - Done with Aviral - November 10, 2011
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/* Question 3: Implement RSA Cryptosystem. */ | |
/* | |
Call keygen function first. | |
Use the key generated to encrypt and decrypt message using | |
corresponding functions. | |
*/ | |
fastexp(a, x, n) = { | |
c = 0; | |
d = 1; | |
m = binary(x); | |
i = length(m); | |
while( (i>0), | |
c = 2 * c; | |
d = (d*d) % n; | |
if( ( m[i]==1 ), | |
c = c + 1; | |
d = (a*d) % n; | |
); | |
i = i - 1; | |
); | |
return(d); | |
} | |
rsaen(p, e, n) = { | |
C = fastexp(p, e, n); | |
print("Encrypted value is ", C); | |
} | |
rsadec(c, d, n) = { | |
p = fastexp(c, d, n); | |
print("Decrypted value is ", p); | |
} | |
/* p, q are large distinct prime numbers */ | |
rsakeygen(p, q) = { | |
n = p * q; | |
phi = (p-1) * (q-1); | |
e = random(phi); | |
while( gcd(e,phi) != 1, | |
e = random(phi) | |
); | |
d = 1; | |
while( ( ((e*d) % phi) != 1 ), | |
d++; | |
); | |
print("Public key is n = "n", e = " e); | |
print("Private key is d = " d); | |
} |
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