How can I compute "r" from: c = g^m * r^N mod N^2 How can I compute "r" from: c = g^m * r^N mod N^2, when all values except r are known? This is the encryption scheme for the paillier cryptosystem. The ciphertext c, plaintext m, and the public key <n, g> is known and I need to find the integer r used for the encryption. My number theory is a little rusty. Thanks!