For anyone worried about 31 (or 64) steps/rounds of SHA-256 being broken, it's actually not that surprising of a result.
This 2013 paper accomplished something similar, but for a reduced-round SHA-256 with 28 steps: https://eprint.iacr.org/2015/350
It further notes:
> Using a two-block approach we are able to turn a semi-freestart collision into a collision for 31 steps with a complexity of at most 2^65.5
So further breakages at 31 steps are somewhat expected.
Tony Arcieri 🌹🦀 /
npub1es…2z8gv
2024-03-29 02:56:18
Author Public Key
npub1ese6na4ymxez6faql2zmqwp5f6vt5rc0zkhd54ykxwezk7ucry9sq2z8gvPublished at
2024-03-29 02:56:18Event JSON
{
"id": "3a0a438bf283f2a4d468d8e5c8746d92757a6d1368425c83de5d5e776fe031d2",
"pubkey": "cc33a9f6a4d9b22d27a0fa85b038344e98ba0f0f15aeda549633b22b7b98190b",
"created_at": 1711680978,
"kind": 1,
"tags": [
[
"proxy",
"https://mas.to/users/bascule/statuses/112176724605914616",
"activitypub"
]
],
"content": "For anyone worried about 31 (or 64) steps/rounds of SHA-256 being broken, it's actually not that surprising of a result.\n\nThis 2013 paper accomplished something similar, but for a reduced-round SHA-256 with 28 steps: https://eprint.iacr.org/2015/350\n\nIt further notes:\n\n\u003e Using a two-block approach we are able to turn a semi-freestart collision into a collision for 31 steps with a complexity of at most 2^65.5\n\nSo further breakages at 31 steps are somewhat expected.",
"sig": "6e3b22158f3fb5b889d2cb9a920c7b5fe724d4e651ca280a81c1ef2807b8ae46209186fb45b393ea351442507d972ef7a9ab0ba70160342421a1b01d6791fecd"
}