Computer efficient linear feedback shift register

A stream cipher cryptosystem comprising:

• pseudo-random bit generator receiving a key and providing a keystream, the pseudorandom bit generator including:
• a linear feedback shift register (LFSR) having a state and including:
• N storage elements together storing N bits of binary data which are separated into w words having word length M and including T tap sources, each tap source providing binary data having a number of bits which is a multiple of M;
• a linear feedback function coupled to the T tap sources and providing a temporary storage word which is a linear function of the binary data provided from the T tap sources;
• and
• wherein the LFSR state is advanced by shifting the binary data in the storage elements by a multiple of M bits using register or location renaming and providing the temporary storage word to fill in storage elements that would otherwise be empty from the shifting;
• and
• a cryptographic combiner for combining a first binary data sequence and the keystream to provide a second binary data sequence.

A method of generating a pseudo-random number, the method comprising the steps of:

• storing N bits of binary data in storage locations in a linear feedback shift register (LFSR), wherein the N bits of binary data are separated into w words having word length M;
• providing T tap sources of binary data from the N bits of binary data, each tap source providing binary data having a number of bits which is a multiple of M;
• providing a temporary value, having a number of bits which is a multiple of M, which is a linear function of the binary data provided from the T tap sources;
• shifting the stored binary data by a multiple of M bits using register or location renaming;
• and
• providing the temporary value to fill in storage locations that would otherwise be empty from the shifting step.