Cryptographic Rsa the Technical Newsletter of Rsa Laboratories, a Division of Rsa Data Security, Inc

1. A leading 0x00 is in the block to be RSA encrypted, ensuring the encryption block is less than the RSA modulus. 2. A block type encoded octet of 0x02 follows the leading 0x00, indicating the block is to be encrypted using a public key. 3. At least eight non-zero pseudorandom padding octets (bytes) are appended to the right after the block type octet. The padding octets should be generated independently for each RSA encryption, especially if the same key is being encrypted. This thwarts Hastad’s attack [6] and allows use of a low value (e.g., 3) for the public Don B. Johnson and Stephen M. Matyas IBM Cryptography Center of Competence, MS P330 522 South Road Poughkeepsie, NY 12601 USA