[p2p-hackers] BitWeav: open P2P micropublishing

[CodesInChaos]

Bitcoin only uses RIPEMD160(SHA256(x)) only in places where the relevant
attack is a second pre-image, not a collision. If neither hashfunction is
pathological, the pre-image resistance of this construction can't be broken
without breaking both hashes. So this construction isn't that silly.

>  As for length extension attacks, I don't believe I should be concerned,
should I? The transfer of messages within the network is dependent on a
defined protocol, so any extra bytes would just be interpreted as a
malformed message.

If you use it in a broken construction, you should be concerned. If you're
not, then there is little reason to worry.

Length extensions are only a problem with a few specific constructions. In
particular using SHA256(k||m) as MAC is broken. If you want a hash based
MAC with SHA-2, use HMAC instead.

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Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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