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

> "The problem case is where someone in a contract setup shows you a script, which you accept as being a payment to yourself. An attacker could use a collision attack to construct scripts with identical hashes, only one of which does have the property you want, and steal coins. > > So you really

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

On Thu, Jan 7, 2016 at 6:52 PM, Pieter Wuille 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

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

So just because other attacks are possible we should weaken the crypto we use? You may feel comfortable weakening crypto used to protect a few billion dollars of other peoples' money, but I dont. On 01/07/16 23:39, Gavin Andresen via bitcoin-dev wrote: > Thanks, Ethan, that's helpful and I'll

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

>Ethan: your algorithm will find two arbitrary values that collide. That isn't >useful as an attack in the context we're talking about here (both of those >values will be useless as coin destinations with overwhelming probability). I'm not sure exactly the properties you want here and

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

On Thu, Jan 7, 2016 at 8:26 PM, Matt Corallo wrote: > So just because other attacks are possible we should weaken the crypto > we use? You may feel comfortable weakening crypto used to protect a few > billion dollars of other peoples' money, but I dont. > No... I'm

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

Indeed, anything which uses P2SH is obviously vulnerable if there is an attack on RIPEMD160 which reduces it's security only marginally. While no one thought hard about these attacks when P2SH was designed, we realized later this was not such a good idea to reuse the structure from P2PKH. Hence

Re: [bitcoin-dev] SegWit testnet is live

Not strictly speaking a wallet but we (BlockCypher) will also go down the segwit path as soon as the BIP and branch are mature enough. All transactions built from our APIs should eventually be segwitted (just made up a verb). Thanks, Matthieu *CTO and Founder, Blockcypher* I have been informed

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

Based on current GH/s count of 775,464,121 Bitcoin tests 2^80 every 19 days. log2(775464121*(1000*1000*1000*60*60*24*19)) = ~80.07 I don't fully understand the security model of segwit, so my analysis will assume that any collision is bad. >But it also requires O(2^80) storage, which is utterly

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

Maybe I'm being dense, but I don't see why 2**80 storage is required for this attack. Also, I don't see why the attacker ever needs to get the victim to accept "arbitrary_data". Perhaps I'm wrong about how the collision attack works: 1. Create a script which is perfectly acceptable and would