Subject: Re: [bitcoin-dev] Time to worry about 80-bit collision attacks or not?

From: Watson Ladd <[email-masked]>
Date: Thu, 7 Jan 2016 17:27:02 -0800

On Jan 7, 2016 5:22 PM, "Gavin Andresen via bitcoin-dev" <
[email-masked]> wrote:
>
> On Thu, Jan 7, 2016 at 6:52 PM, Pieter Wuille <[email-masked]>
wrote:
>>
>> Bitcoin does have parts that rely on economic arguments for security or
privacy, but can we please stick to using cryptography that is up to par
for parts where we can? It's a small constant factor of data, and it
categorically removes the worry about security levels.
>
> Our message may have crossed in the mod queue:
>
> "So can we quantify the incremental increase in security of
SHA256(SHA256) over RIPEMD160(SHA256) versus the incremental increase in
security of having a simpler implementation of segwitness?"

There are several clever ways to exploit even chosen prefix collisions
using the scripting language. One could search for collisions where one
message is some data and the other is a jump over a critical check.

>
> I believe the history of computer security is that implementation errors
and sidechannel attacks are much, much more common than brute-force breaks.
KEEP IT SIMPLE.

Ask the Iranian nuclear program. Or those brainwallet users.
>
> (and a quibble:  "do a 80-bit search for B and C such that H(A and B) =
H(B and C)"  isn't enough, you have to end up with a C public key for which
you know the corresponding private key or the attacker just succeeds in
burning the funds)
>
>
> --
> --
> Gavin Andresen
>
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