Travis H. wrote:

- Stream ciphers (additive)This reminds me, when people talk about linearity with regard to a function, for example CRCs, exactly what sense of the word do they mean? I can understand f(x) = ax + b being linear, but how exactly does XOR get involved, and are there +-linear functions and xor-linear functions? Are they disjoint? etc.

If you have a linear algebra book handy, look up "linear transformation".

`Briefly, a function T from a vector space V to another vector space W`

`(where V and W are defined over the same field) is called a`

linear transformation if it satisfies i) T(u +_V v) = T(u) +_W T(v) ii) T(c *_V u) = c *_V T(u) iii) T(0_V) = 0_W CRC is a linear transformation because CRC(u + v) = CRC(u)+CRC(v). -James --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]