n1ghtf1re/public-key-ciphers

The implementation of the public key ciphers: Elgamal

Public-Key-Ciphers

About the library

The library contains one public key ciphers: Elgamal

Class Elgamal:

Constructors:

• Elgamal(long p, long x, long k) . p - prime number, x - Private key, number of range (1; p - 1), Session key, mutually prime with p number of range (1; p - 1)

Methods:

• encrypt(byte[] plaintext) - Encodes an array of bytes
  • One byte of source array turns into two elements of the array of ints.
    • CIPHERTEXT[i] = g^k mod p
    • CIPHERTEXT[i+1] = (y^k * PlAINTEXT[i/2]) mod p
• decrypt(byte[]) - Decodes an array of ints
  • Two elements of ciphertext array (int[]) turns into one byte of plaintext array
    • (b = ciphertext[i + 1], a = ciphertext[i])
    • PLAINTEXT[i/2] = ( b * (a^x)^-1 ) mod p = (b * (a^x)^(phi(p) - 1)) mod p, phi - Euler function
• getPublicKey() - return Public Key object (p, g, y)