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Re: More 40-bit RC4 nonsense
In article <[email protected]>, you write:
> -----BEGIN PGP SIGNED MESSAGE-----
>
> If I recall correctly, the first byte out of the RC4 stream has
> about a 40% chance of being the first byte of the key. Thus, if the
> 40-bit "secret" part of the key is the _beginning_ of the full 128-bit
> key, then the keyspace is effectively reduced by about seven bits,
> meaning that I would be able to crack a key on my PC in a couple of
> days or so.
> Of course, if the "clear" 88 bits went first, there would be no
> advantage whatsoever. The SSL document very carefully does not say
> how they combine the two key parts to form the 128-bit key. Does
> anyone know?
>
> Raph
>
> -----BEGIN PGP SIGNATURE-----
> Version: 2.6
>
> iQCVAwUBLu3cI/4BfQiT0bDNAQEToQQAtcy2v0sBd+g5GBrm+Pa1AykqS4tTctfu
> EYga7kPry4wvGmI7/HpD+SVVDQRcJe+O9CxH9cpvRgBRIBhyvsFXVBSTW0OTJgXb
> 1bYh5qerD5J/gXAs0XWIp0+Hj8GqeTIRkFTseU4MDcDfQ7tOSEFvul97iSNYIytX
> AMkmAEmMXxU=
> =S80T
> -----END PGP SIGNATURE-----
OOPS. This is a spec ommission. The clear key data (aka "salt") is
combined with the secret portion as follows:
The bytes of the salt are concatenated with the secret
portion with the secret portion making up the least significant
bytes of the concatenation.
I will spec'ize the english...
By the way, where did this 40% number come from? For some reason RSA
never told me this... :^(
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Kipp E.B. Hickman Netscape Communications Corp.
[email protected] http://www.mcom.com/people/kipp/index.html