Encryption Decryption Question:

The Rabin signature scheme is a variant of the RSA signature scheme. It has the advantage over RSA that finding the private key and forgery are both provably as hard as factoring. Verification is faster than signing, as with RSA signatures. In Rabin's scheme, the public key is an integer n where n = pq, and p and q are prime numbers which form the private key. The message to be signed must have a square root mod n; otherwise, it has to be modified slightly. Only about 1/4 of all possible messages have square roots mod n.