DEVICE AND METHOD FOR IMPLEMENTING A CRYPTOGRAPHIC HASH FUNCTION

摘要

A computing device and a computing device implemented method are provided for preparing a message a bit-length number of bits in length less than or equal to a pre-determined maximum size, for input to a cryptographic hash function operating on blocks of a predetermined block size of B bits. The computing device comprises a processor in communication with a memory for processing the message. The method comprises the processor padding the message by adding sufficient padding bits and a length block of length n bits, such that a padded bit-length of the padded message is an integer factor times the block size B; and the processor setting the bits of the length block such that if the bit-length is less than 2 n bits long, the bits of the length block represent the padded bit-length; and, if the bit-length is greater than or equal to 2 n bits long, the bits of the length block represent a pre-determined value non-representative of the bit-length.