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RSA-Algorithm

Crypto-text generator using RSA public-key crypto-system

  • The first task we hit is to calculate a fairly small number (e) that shares no factors (m)

    • m = (P-1)*(Q-1)

  • Now, find e such that greatest common divisor (GCD) of e and m is 1.

    • ULONG gcd(ULONG x, ULONG y)

  • Next: Find the integer d, such that: (d * e) % m == 1 this is called the "modular congruence" of e and m. To do that, we will use another version of the GCD function known as "Euclid's Extended Algorithm. I could have overloaded the name; however, I don't want them confused, so I will name them differently.

    • ULONG gcdExtended(ULONG a, ULONG b, ULONG* x, ULONG* y)

  • Now, the gcdExtended will be used to calculate the modular congruence. (These are a pair.)

    • ULONG modularCongruence(ULONG a, ULONG m)

  • Finally, we will need to compute (A^B)%C which is the heart of the RSA algorithm.

    • ULONG computeRsa(ULONG a, ULONG b, ULONG c)