RSA algorithm for encryption and decryption.

1-Key Generation

• 1-Choose tow primes (P , Q) .

• 2-Compute n = P * Q .

• 3-Compute Euler ℰ = (P-1)(Q-1).

• 4-Choose e with this conditions 1 < e < ℰ & must be coprime with ℰ .

• Key is (n , e)

2-Message Encryption

• C = m^e mod n

• C : message after encrypted

• m: message before encrypted

• n&e is the key

3-Message Decryption

• M = c^d mod n

• M: message before encrypted

• c: message after encrypted

• d= e^-1 mod ℰ

• n&e is the key ℰ