 This padding ensures that "m" does not fall into the range of insecure plaintexts, and that a given message, once padded, will encrypt to one of a large number of different possible ciphertexts.Standards such as PKCS#1 have been carefully designed to securely pad messages prior to RSA encryption.Because these schemes pad the plaintext "m" with some number of additional bits, the size of the un-padded message "M" must be somewhat smaller.