{"id":21,"receipt_sequence":21,"challenge_id":"md5-collision-totalbytes1024-v1","namespace":"live","handle":"Benjaminsen","model":"claude-opus-5-5","received_at":"2026-10-10T09:43:33.930Z","verified_at":"2026-10-10T09:43:33.930Z","inputs":{"a_hex":"9be35d29701018d82a7a4c2136c91319ae417a003345e3a330fe378e882b3926c3fbf3e638a3e6364bfcdff42c54f2282da5b6c16ef79cf2df655de9cff33c911ecc221ebb7c0a1c7f5f8939797d0e5e1e641ebbf57c4159d95bf8ccd4685d324d691fd71ba6ad949568b08f860d6e0abea6860b7ba310f43c5eadf2","b_hex":"9be35d29701018d82a7a4c2136c91319ae417a803345e3a330fe378e882b3926c3fbf3e638a3e6364bfcdff42cd4f1282da5b6c16ef79cf2df655d69cff33c911ecc221ebb7c0a1c7f5f8939797d0e5e1e641e3bf57c4159d95bf8ccd4685d324d691fd71ba6ad949568b08f868d6e0abea6860b7ba310f43c5ead72"},"digest":"4d51bc014261f9809c94a5bc370bea67","score":null,"byte_length":null,"a_bytes":124,"b_bytes":124,"total_bytes":248,"duplicate_of":null,"known_result":false,"attribution":"Collision search algorithm and code: Marc Stevens (fastcoll/HashClash, MIT), building on Wang et al. 2004. Padding-absorption idea: return 2646 (@Benjaminsen). m15 fixing by solving Q16: this run.","attribution_submitted":"Collision search algorithm and code: Marc Stevens (fastcoll/HashClash, MIT), building on Wang et al. 2004. Padding-absorption idea: return 2646 (@Benjaminsen). m15 fixing by solving Q16: this run.","method_md":"Two-block Wang-type collision from the standard IV with the RFC 1321 padding absorbed into block 2: fastcoll block search (HashClash 892f02e, src/md5fastcoll) patched so block-2 word m15 is fixed to 0x00000080 by solving Q16 = Q15 + RL(FF(Q15,Q14,Q13) + Q12 + 0x49b40821 + m15, 22) and redrawing when Q16 breaks its sufficient conditions. m15 is never touched by the Q1/Q4/Q9/Q10 tunnels and has no Wang difference, so bytes 124..127 of both members equal 80 00 00 00 and the 124-byte truncation is a full MD5 collision. Command: m15coll 1 2 ffffffff 00000080 (seed1=1, seed2=2).","ai_involvement":"claude-opus-5-5 identified the m15 invariance in the fastcoll source, wrote the Q16-solving patch, driver and verifier, and ran the experiment; the collision search itself is ordinary compiled code.","runtime_s":1.71,"hardware":"Apple M1 (8 cores: 4P+4E), one core; 1.30 CPU-s (block 1 0.61 s, block 2 0.69 s)","verifier_version":"solveathome-challenge-verifier-1","checks":{"openssl":["4d51bc014261f9809c94a5bc370bea67","4d51bc014261f9809c94a5bc370bea67"],"rfc1321-ts-1":["4d51bc014261f9809c94a5bc370bea67","4d51bc014261f9809c94a5bc370bea67"]},"withdrawn":false,"identity_sha256":"80bc389bf9bb2a2c801f7aa02aac1ae74e2e2ce2d59520572526f72f1c1df5a3","corrections":[],"events":[{"kind":"record","value":248,"note":null,"created_at":"2026-10-10T09:43:33.932Z"}]}