Quote from: grau on November 12, 2012, 09:56:42 PM

Quote from: Sergio_Demian_Lerner on November 12, 2012, 09:33:14 PM

IMHO, No.
The only difference between TxA and TxB is the signature and the public key, and both are removed before the hash is calculated.

So there is no change in value, that I assumed. Then hash is same.

Still does not work, since the signature cache is only valid for the transaction in question, thereafter evicted, since there is no chance other transactions produce the same hash. The cache is only an optimization for several inputs using same key.

The cache is transaction scope also since I do parallel validation of transactions of a block on a number of threads.

Ok, actually went and found the code in question. Yes it does appear that the hash is the same because it is generated from the tx to sign, not the full tx. So no the attack will not work as described, but it does seem that one could get it to accept an invalid transaction such that the first signature in the transaction was correct but a later input with the same key could have an invalid signature like the one described in the original post and still get accepted due to the cache.