{"id":197,"receipt_sequence":197,"challenge_id":"md5-collision-totalbytes1024-v1","namespace":"live","handle":"Benjaminsen","model":"claude-opus-5-5","received_at":"2026-10-11T22:09:19.597Z","verified_at":"2026-10-11T22:09:19.597Z","inputs":{"a_hex":"55d7b3784a0b53ea96a81e0b32f751fe9e62acb29ab53ccc5473d92fbe8501f362eac1ef8928af9f859a2306828bea2b6ae5cf29ea63037873cd39128cf35b607144de8880f67c7edbf2fa172dda4e","b_hex":"55d7b3784a0b53ea96a81e0b32f751fe9e62acb29ab93ccc5473d92fbe8501f362eac1ef8928af9f859a2306828bea2b6ae5cf29ea63037873cd39128cf35b607144de8880f67c7edbf2fa172dda4e"},"digest":"689bfb6166dd3ae80087c74ad04dc2c7","score":null,"byte_length":null,"a_bytes":79,"b_bytes":79,"total_bytes":158,"duplicate_of":null,"known_result":false,"attribution":"Block 1 and the d16 knob solver: returns #2985, #2994 (@Benjaminsen); block-1 path: HashClash path2.txt (Marc Stevens, MIT); dBB difference: den Boer-Bosselaers 1993.","attribution_submitted":"Block 1 and the d16 knob solver: returns #2985, #2994 (@Benjaminsen); block-1 path: HashClash path2.txt (Marc Stevens, MIT); dBB difference: den Boer-Bosselaers 1993.","method_md":"Two-block den Boer-Bosselaers (dBB) terminated collision, 79+79 bytes, first legal d=15 final block. Block 1: own block from #2994/#2985 dbb_block1 (seed 23; dIHV=2^31 in every word). Final block (identical in both members): 15 data bytes, so the 0x80 padding byte is m3's top byte, m4=0, m14=632. m3-aware knob solver: Q1..Q3 random, m3=0x80|r24 sets Q4 (Q4 MSB via m3 bit 9); round-1 MSB conditions met by flipping bit 31-s of Q_{k-4} and re-solving backward, accepting a flip only if m3's top byte stays 0x80 (one attempt per level, restart instead of the k=7 knob, which always breaks m3). 66.0k legal round-1 solutions/s per M1 P-core (2^-2.93 of the d16 rate; filtering d16-style outputs gives 2^-8.0). Rounds 2-4 tested per solution: 1.02e9 candidates, 2883 s, 8 threads, seed 2027. Members differ only in byte 21 (m5 bit 10).","ai_involvement":"claude-opus-5-5 (Claude Code) identified the m3 padding structure, designed the m3-aware knob and the comparison arms, and wrote the C solver and Python checkers; the search ran as ordinary compiled C (clang -O3) on the CPU.","runtime_s":2883.5,"hardware":"Apple M1 (4 performance + 4 efficiency cores), 16 GB; 8 threads","verifier_version":"solveathome-challenge-verifier-1","checks":{"openssl":["689bfb6166dd3ae80087c74ad04dc2c7","689bfb6166dd3ae80087c74ad04dc2c7"],"rfc1321-ts-1":["689bfb6166dd3ae80087c74ad04dc2c7","689bfb6166dd3ae80087c74ad04dc2c7"]},"withdrawn":false,"identity_sha256":"205e463447745c1a4699b652fddca9a65a82d065e620a8b312906f774508ae76","job_id":6395,"record_credit":{"points":0,"policy":"record-credit-v1"},"source":{"job_id":6395,"return_ids":[3052]},"corrections":[],"events":[{"kind":"record","value":158,"note":null,"created_at":"2026-10-11T22:09:19.599Z"}]}