[25654] in cryptography@c2.net mail archive
Re: the meaning of linearity
daemon@ATHENA.MIT.EDU (Florian Weimer)
Mon May 15 17:33:32 2006
X-Original-To: cryptography@metzdowd.com
X-Original-To: cryptography@metzdowd.com
From: Florian Weimer <fw@deneb.enyo.de>
To: "Travis H." <solinym@gmail.com>
Cc: Cryptography <cryptography@metzdowd.com>
Date: Mon, 15 May 2006 07:33:25 +0200
In-Reply-To: <d4f1333a0605141739r110a2d99v87d75546cc99376@mail.gmail.com>
(Travis H.'s message of "Sun, 14 May 2006 19:39:30 -0500")
* Travis H.:
> 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,
I wouldn't call that "linear" if b /= 0, "affine" is probably better.
But I'm not familiar with the cryptographic term, maybe it's
different.
> but how exactly does XOR get involved, and are there +-linear
> functions and xor-linear functions? Are they disjoint? etc.
It refers to arithmetic over GF(2), the field with two elements. In
this field, XOR is addition, and AND is multiplication.
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