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Summary

There are several cryptographic standard algorithms, used for encryption, decryption, and authentication. Some of those algorithms have been implemented, and results are given in the tables below.

The most important characteristics are the following:

• The key size, typically expressed as a number of bits (encryption and decryption)
• The digest size, typically expressed as a number of bits (hashing)
• The data bit rate. A typical values is 10 Mbit/s.
• Code can be optimised for size or for speed - with very different results. Results reported here are optimised for speed at the expense of memory.

module_AES

A function running inside a single thread can encrypt and decrypt data as follows (assuming 8 threads on a 400 MHz part - or 50 MIPS threads):

Functionality	Key size	Data rate	Memory	Status
Encryption	128 bit	6.8 Mbit/s	8K	Implemented and tested
Decryption	128 bit	9.1 Mbit/s	13K	Implemented and tested

Note that decryption has been severely optimised - encryption can probably be optimised to a similar level. Multiple blocks that have the same key can be decrypted in parallel in multiple threads with only marginal extra memory requirements. Encryption in parallel is only feasible if there is no chaining between subsequent blocks.

In order to achieve the data rate given above, key must be expanded once, prior to decrypting a large number of blocks.

module_SHA2

The SHA2 module has two interfaces: one that is a function call from within a single thread, and one that requires a separate thread to do the groundwork, which acts as a server. The performance is as follows: (assuming 8 threads on a 400 MHz part - or 50 MIPS threads):

Functionality	Hash size	Data rate	Memory	Status
Block based	256 bit	3.5 Mbit/s	4.5K	Implemented
Separate thread	256 bit	4.0 Mbit/s	4.5K	Implemented