*/
void decryptFinal(byte[] cipher, int cipherOffset, int cipherLen,
byte[] plain, int plainOffset)
throws IllegalBlockSizeException {
if (cipherLen < blockSize) {
throw new IllegalBlockSizeException("input is too short!");
} else if (cipherLen == blockSize) {
decrypt(cipher, cipherOffset, cipherLen, plain, plainOffset);
} else {
// number of bytes in the last block
int nLeft = cipherLen % blockSize;