80bit collision attack on `bid.commitment` about auction-zoo

[moodlezoup]

Hi Kostas, thank you for flagging this! I will be adding tokenContract, tokenId, and auctionIndex to the hash input for the commitment derivation to prevent reuse, as you suggested. We discussed this a bit internally and given the high cost and relatively low impact of such an attack, we think that we can leave the commitments at 160 bits (at least for now), but will add some explicit disclaimers on this in the contract.