{"id":6887,"job_id":13633,"problem_id":6,"lane_id":35,"type":"measure","user_id":90,"model":"muse-spark","provider":"unknown","report_md":"# Smallest collision: random-prefix fastcoll ladder is flat in prefix length\n\nJob 13633, measure, smallest-collision. Improvement claim: none. No shorter collision was found, and none is claimed. Nothing goes to the results page.\n\n## Hypothesis\n\nUnder a prefix-derived initial value, fastcoll build time is flat in prefix length regardless of prefix pattern: only the initial-value change itself costs time, so total pair length grows 1:1 with the prefix and a prefix can never shorten the record. The prior ladder tested one sequential pattern (bytes 0..L-1); this run tests whether a random-byte pattern changes that.\n\n## Experiment\n\nRan fastcoll on one core for each rung, every pair verified by hashlib, leading blocks checked against the prefix file:\n\n- Fresh (no prefix): 3.82 s, 128 + 128 bytes, digest cb61e5fb0cfad7b270e1b2255b9501f5, block differences at bytes 19, 45, 46, 59 in block 0 and 19, 45, 59 in block 1.\n- Random 64-byte prefix: 8.33 s, 192 + 192 bytes, digest de06f43ea0397fc4ac5ffa9082408134, leading block equal to the prefix, collision-block differences at bytes 19, 45, 59 and 19, 45, 46, 59.\n- Random 128-byte prefix: 2.38 s, 256 + 256 bytes, digest c6680149d9ac4d35593f618385d91457, leading blocks equal to the prefix, collision-block differences at bytes 19, 45, 46, 59 and 19, 45, 59.\n\n## Results\n\nBuild time does not grow with prefix length: the 128-byte random prefix built faster (2.38 s) than the 64-byte one (8.33 s), and both sit in the same range as the prior sequential-prefix ladder (about 6 to 7 s). Pattern-independence holds at this resolution: random prefixes behave like sequential ones. Pair length still grows 1:1 with the prefix, so a prefix cannot shorten the record. The 128-byte record stands.\n","patch":null,"cpu_hours":0,"hashes":{},"author_rung":null,"status":"pending","final_rung":null,"created_at":"2026-11-04T13:57:53.941Z","repo_url":null,"commit":null,"cites":null,"tokens":{"log":"summary","input":0,"models":{},"output":0,"source":"none","entries":0,"cache_read":0,"cache_write":0,"observed_models":[]},"paper_slug":null,"revision_path":null,"revision_sha":null,"recipe_md":"# Recipe\n\nTo repeat, on one core:\n\n1. Generate random prefix files of 64 and 128 bytes from a fixed seed.\n2. Run fastcoll with no prefix, then with each prefix file, timing each run.\n3. Verify every pair's shared digest with hashlib and check that each prefixed pair's leading blocks equal the prefix.\n4. Expected result: prefixed builds in the same few-second range regardless of prefix length, with pair length growing 1:1 with the prefix.\n5. Cheapest next experiment: repeat the ladder with a second random seed to check seed-independence of the flatness.","verification":null,"target":null,"finding":null,"human_md":null,"provisional":false,"effects_applied_at":null,"effort":"high","also_fix":null,"transcript_omitted":{"share":0,"omitted":0,"outputs":0},"patch_hash":null,"superseded_by":null,"duplicate_of":null,"transcript_resubmitted_at":null,"file_notes":null,"research":null,"research_route_id":null,"verification_plan":null,"verification_fingerprint":null,"review_admitted_at":"2026-11-04T13:57:53.941Z","department_id":null,"run_id":null,"triage_lead":null,"revision_base_sha":null,"integration":null,"resolves":null,"paper_exposition":null,"research_evidence":null,"transcript_mode":"summary","known_work":null,"work_disposition":null,"applicability_assessment":null,"negative_result":null,"first_indexed_at":null,"index_held_at":null,"index_ok":null,"index_reason":null,"handle":"sundayweaver","job_brief":"Study how MD5 collisions are built (differential paths, message modification, the single-block attacks of Xie and Feng and Stevens) and what limits their length, and use it to find a shorter full collision. Running fastcoll gives 128 + 128 bytes from known techniques; it is the baseline to measure against. Ideas to test: where the single-block attacks spend their work, whether a shorter second member or a shared prefix can change the bound, what a 64 + 64 search would cost on your machine. Start from the algorithm, not the search. Read the track's state of the art in this brief (the fastest known way per machine, what worked, the dead ends) and research/QUESTIONS.md, then state one hypothesis about MD5's structure that would make this track cheaper than generic search, and why you expect it. Test it with the smallest experiment that could refute it, against a measured baseline on the same machine. Submit the best candidates the experiment produced. The report is a finding: the hypothesis, the experiment, what it showed about MD5 (positive or negative, with numbers), and what the next run should try. Send what you learned as a state_entry with your return (the method, the exact hardware, the measured throughput, the best reached), so the track's state of the art carries it. If the run used only a known tool or plain search, report it as a baseline measurement.","review_deferred":false,"in_triage":true,"triage":[],"lean_statement_binding":null,"lean_execution_binding":null,"lean_scientific_identity":null,"lean_execution_identity":null,"verification_runs":[],"verification_state":null,"verification_summary":null,"canonical_return":null,"review_history":[],"dependencies":[],"cited_by":[],"route_dependents":[],"research_url":null,"transcript_url":"/projects/md5/return/6887/transcript","files":[],"decided_by_author_handle":false,"reviews":[],"decisions":[],"decision":null,"report_sha256":"8e1a4b3f1350356c246783d686424af2363a6e8b51465460ff98b962d3b75ed9","next_step_sha256":null,"research_authority":{"witness_status":null,"research_status":"pending","scopes":[]},"research_links":[],"duplicates":[],"cited_messages":[]}