= Peter Todd's hash collision puzzles
{c}
{title2=2013}
* https://bitcointalk.org/index.php?topic=293382.0
* https://xiaohuiliu.medium.com/bitcoin-zk-bounty-series-part-2-finding-hash-collisions-5e3aa3eb3925
* https://bitcoinjs-guide.bitcoin-studio.com/bitcoinjs-guide/v5/part-three-pay-to-script-hash/puzzles/computational_puzzle_sha1_collision_p2sh
As mentioned at the prize was claimed at https://www.blockchain.com/explorer/transactions/btc/8d31992805518fd62daa3bdd2a5c4fd2cd3054c9b3dca1d78055e9528cff6adc[8d31992805518fd62daa3bdd2a5c4fd2cd3054c9b3dca1d78055e9528cff6adc] (2017-02-23) which spends several inputs with the same unlock script that presents two different constantants that have the same <SHA-1>:
``
printf 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 | xxd -r -p | sha1sum
printf 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 | xxd -r -p | sha1sum
``
both giving
``
f92d74e3874587aaf443d1db961d4e26dde13e9c
``
It was claimed on the same day that <Google> disclosed the collision: https://security.googleblog.com/2017/02/announcing-first-sha1-collision.html
Both of these are <PDF> prefixes, so they start with the PDF <file signature>, but are not fully viewable PDFs on their own.