{"id":172,"receipt_sequence":172,"challenge_id":"md5-collision-totalbytes1024-v1","namespace":"live","handle":"Benjaminsen","model":"claude-opus-5-5","received_at":"2026-10-11T12:41:04.849Z","verified_at":"2026-10-11T12:41:04.849Z","inputs":{"a_hex":"55d7b3784a0b53ea96a81e0b32f751fe9e62acb29ab53ccc5473d92fbe8501f362eac1ef8928af9f859a2306828bea2b6ae5cf29ea63037873cd39128cf35b60b223d37678e41c8430c335bcce3586c5","b_hex":"55d7b3784a0b53ea96a81e0b32f751fe9e62acb29ab93ccc5473d92fbe8501f362eac1ef8928af9f859a2306828bea2b6ae5cf29ea63037873cd39128cf35b60b223d37678e41c8430c335bcce3586c5"},"digest":"9b529dffcc7913d8a46c9010723a5cd4","score":null,"byte_length":null,"a_bytes":80,"b_bytes":80,"total_bytes":160,"duplicate_of":null,"known_result":false,"attribution":"Block-1 path: HashClash path2.txt (Marc Stevens, MIT); block-1 search and dBB final-block trail: returns #2985, #2720 (@Benjaminsen); dBB difference: den Boer-Bosselaers 1993.","attribution_submitted":"Block-1 path: HashClash path2.txt (Marc Stevens, MIT); block-1 search and dBB final-block trail: returns #2985, #2720 (@Benjaminsen); dBB difference: den Boer-Bosselaers 1993.","method_md":"Two-block den Boer-Bosselaers (dBB) terminated collision, 80+80 bytes. Block 1: fresh own unrestricted-byte search on HashClash textcoll path2 (dm5=+2^10) with a 23-bit Q9 tunnel (#2985 dbb_block1, seed 23, 1.8 s, 1 thread); dIHV=2^31 in every word, b31=c31=d31. Final block (identical in both members): 16 data bytes + RFC padding, so m4..m15 are fixed and there is no Q1 tunnel. Round-1 MSB conditions are met by bitwise message modification: on a failed Q_k condition, flip bit 31-s of Q_{k-4}, keep Q_{k-3..k-1}, re-solve Q_{k-5..1} backward through the fixed words and let m0..m3 absorb Q1..Q4 (22.5x the naive round-1 rate). Rounds 2-4 (31 conditions) are tested per round-1 solution: 3.5e8 candidates, 130 s, 8 threads. Members differ only in byte 21 (m5 bit 10).","ai_involvement":"claude-opus-5-5 (Claude Code) chose the route, derived the backward re-solve message modification, and wrote the C search program and Python checker; the searches ran as ordinary compiled C (clang -O3) on the CPU.","runtime_s":132,"hardware":"Apple M1 (4 performance + 4 efficiency cores), 16 GB; 8 threads for the final block, 1 thread for block 1","verifier_version":"solveathome-challenge-verifier-1","checks":{"openssl":["9b529dffcc7913d8a46c9010723a5cd4","9b529dffcc7913d8a46c9010723a5cd4"],"rfc1321-ts-1":["9b529dffcc7913d8a46c9010723a5cd4","9b529dffcc7913d8a46c9010723a5cd4"]},"withdrawn":false,"identity_sha256":"e43b699f640bbb40e745ce0e6f8338f8ba4279e5d4ef1e903469c8f17f5297e9","job_id":6283,"record_credit":{"points":0,"policy":"record-credit-v1"},"source":{"job_id":6283,"return_ids":[2994]},"corrections":[],"events":[{"kind":"record","value":160,"note":null,"created_at":"2026-10-11T12:41:04.851Z"}]}