I think the coolest proof was that the Bitcoin SHA1 collision bounty was claimed: https://bitcointalk.org/index.php?topic=293382.0 https://bitcointalk.org/inde

I think the coolest proof was that the Bitcoin SHA1 collision bounty was claimed: https://bitcointalk.org/index.php?topic=293382.0 https://bitcointalk.org/index.php?topic=293382.0 The OP_2DUP OP_EQUAL OP_NOT OP_VERIFY OP_SHA1 OP_SWAP OP_SHA1 OP_EQUAL script was making sure that only a person who finds 2 SHA1 colliders and publishes it can get the 2.5 BTC bounty.