{"id":2830,"job_id":5963,"problem_id":6,"lane_id":35,"type":"explore","user_id":76,"model":"auto","provider":"unknown","report_md":"# First look (route 261): Stevens md5sbc too slow here for an N≥200 m15 census\n\n**Outcome: inconclusive.** Built and ran Marc Stevens’ published single-block attack (2012 sources). **0 full collisions** in ~14 CPU-minutes on Linux aarch64; therefore the preregistered N≥200 m15=`0x80` rate was not obtained within the route’s ~1 CPU-h budget.\n\n## Experiment\n\n1. Fetched `md5-1block-collision-attack-sources.tar.bz2` from marc-stevens.nl (real bzip2; prior workspace copy was HTML).\n2. Built `md5sbc` with `g++ -O2` (no Boost).\n3. Searched with stock RNG; progress via `Q29ok` (~2^6.5–2^7.1 /s). Peak Q29ok ≈ 65k after ~11 min; still no `Found collision!`.\n4. Additional 3 min instrumented run likewise produced 0 pairs.\n\n## Results\n\n| Metric | Value |\n|---|---|\n| Full colliding pairs | **0** |\n| Approx. search CPU | ~14 min |\n| m15==0x80 fraction | **undefined** (no pairs) |\n| Tool build | OK |\n\n## Obstacle\n\nAttempt failed on sample size: this host/build did not emit enough single-block pairs to estimate p̂(m15=0x80). Revisit with a faster single-block implementation, GPU/SIMD port, or a multi-hour CPU reservation explicitly sized after a first timed collision (record time-to-first-pair, then scale to N=200).\n\n## What this does *not* close\n\nAlgebraic reachability of m15=`0x80` on Stevens’ path, or route 249’s 126-byte construction under a different solver.\n\n## OUTCOMES.md entry (proposed)\n\n| Track | Method | Budget and hardware | Best reached | Note |\n| --- | --- | --- | --- | --- |\n| Smallest collision | Stevens md5sbc m15 census (first look) | ~0.25 CPU-h; aarch64 | 0 pairs / 14 min | Route 261 inconclusive |\n","patch":null,"cpu_hours":0.25,"hashes":{"recipe.md":"7a80a944c14e3ca3bb6ad2acdc868a3b270ee4dde977e97cabb289da76966b24","report.md":"9c0b9e6429435056736f3cbf61e2453e7d7722c719537466619ce647f1b7411f","results.json":"2903e1bf3a06ae80ba583075c80a694df41ce602eed161e6378455a8a4c037a6","md5sbc_run.log":"dca31632529498a950a6e6be9d3622614b27a3a19ff0b9408550f388edd0bb13","md5sbc_sample.log":"ac4a2cce468db28fd6f33f162b99aa376f6dab0715d6c048514f3e1f543f147f","transcript_summary.md":"1dde71b56f897a1c11fd19530a0dcad774b8a42783b17accdaf67a975a74716e"},"author_rung":"measured","status":"recorded","final_rung":"recorded","created_at":"2026-10-10T20:35:14.492Z","repo_url":null,"commit":null,"cites":{"files":["2903e1bf3a06ae80ba583075c80a694df41ce602eed161e6378455a8a4c037a6","9c0b9e6429435056736f3cbf61e2453e7d7722c719537466619ce647f1b7411f","7a80a944c14e3ca3bb6ad2acdc868a3b270ee4dde977e97cabb289da76966b24","1dde71b56f897a1c11fd19530a0dcad774b8a42783b17accdaf67a975a74716e","dca31632529498a950a6e6be9d3622614b27a3a19ff0b9408550f388edd0bb13","ac4a2cce468db28fd6f33f162b99aa376f6dab0715d6c048514f3e1f543f147f"],"handles":[],"returns":[2828,2694,2808],"messages":[]},"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\n```bash\ncurl -fsSLO https://marc-stevens.nl/research/md5-1block-collision/md5-1block-collision-attack-sources.tar.bz2\ntar xjf md5-1block-collision-attack-sources.tar.bz2\ng++ -O2 -o md5sbc main.cpp collisionfinding.cpp md5detail.cpp timer.cpp rng.cpp\n./md5sbc   # wait for \"Found collision!\"; time-to-first-pair unknown on aarch64 here (>14 min)\n```","verification":null,"target":null,"finding":null,"human_md":null,"provisional":false,"effects_applied_at":null,"effort":null,"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":{"outcome":"inconclusive","obstacle":{"kind":"attempt_failed","evidence":"md5sbc_run.log / md5sbc_sample.log progress (Q29ok rates ~2^6.5-2^7.1/s); results.json.","statement":"Could not measure the fraction of single-block colliding pairs with m15=0x00000080 among N>=200 pairs: the Stevens 2012 md5sbc tool emitted 0 full collisions in ~14 CPU-minutes on Linux aarch64/g++-O2.","assumptions":"Stock md5sbc from marc-stevens.nl sources; default RNG; no Boost maxruntime; single core.","revisit_when":"A timed first collision on this host (or a faster single-block solver) so N=200 cost can be budgeted; or an algebraic proof that the path forbids/allows m15=0x80."},"route_id":261,"depends_on":[2828,2694],"evidence_md":"results.json: Stevens md5sbc built OK; 0 full collisions in ~14 CPU-min (Q29ok peak 65536). N>=200 m15 rate undefined within 1 CPU-h."},"research_route_id":261,"verification_plan":null,"verification_fingerprint":null,"review_admitted_at":null,"department_id":"dept_fa6dbf79354b8806abb61eec","run_id":"run_a7419dd35088e539169f2abb","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,"handle":"aasper03","job_brief":"Search online for existing attempts, results, tables and datasets before testing feasibility. Reuse the recorded search and inspect the closest sources and weakest assumption. Use published numbers with citations; do not reproduce them in a first look. Seek the smallest experiment on the uncovered step. Recommend promising only with specific evidence and a bounded next step; do not claim the route is proved. Map the assumptions of any borrowed method onto this problem.\n\nRead GET <project base>/research-routes/261 and return #2828. Return the ordinary report and transcript plus research: {route_id: 261, outcome: \"promising|progress|blocked|inconclusive|known|result\", evidence_md: \"what the evidence changes, <=4000 chars\", prior_art_md: \"updated online search record, sources and exact remaining gap, <=4000\", next_step: {question, method, success, failure, budget_hours} <only for continued pursuit; what to do, never when or how fast; it must not ask for what a return on this route or a linked route already did, and the route returns it builds on go in depends_on or cites.returns>, obstacle: {kind, statement, assumptions, evidence, revisit_when} <for blocked/inconclusive>, depends_on: [<return ids actually required>]}. A result with a distinct next_step requests review and continues pursuit concurrently; omit next_step when no further experiment is warranted. Use known with prior_art_md and no next_step or obstacle when cited prior work already covers the proposed contribution; it stops automatic investigation without requesting review. The evidence grade is separate. Do not close a broad route because one proof attempt failed.","review_deferred":false,"in_triage":false,"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":[{"id":"2694","status":"accepted","final_rung":"verified","canonical_return_id":null},{"id":"2828","status":"recorded","final_rung":"recorded","canonical_return_id":null}],"cited_by":[{"id":2831,"handle":"aasper03","status":"accepted"},{"id":2838,"handle":"aasper03","status":"recorded"},{"id":2840,"handle":"aasper03","status":"pending"},{"id":2857,"handle":"aasper03","status":"pending"},{"id":2858,"handle":"aasper03","status":"pending"}],"route_dependents":[261,263,265],"research_url":"/projects/md5/research-routes/261","transcript_url":"/projects/md5/return/2830/transcript","files":[{"sha256":"2903e1bf3a06ae80ba583075c80a694df41ce602eed161e6378455a8a4c037a6","name":"results.json","bytes":859},{"sha256":"9c0b9e6429435056736f3cbf61e2453e7d7722c719537466619ce647f1b7411f","name":"report.md","bytes":1646},{"sha256":"7a80a944c14e3ca3bb6ad2acdc868a3b270ee4dde977e97cabb289da76966b24","name":"recipe.md","bytes":359},{"sha256":"1dde71b56f897a1c11fd19530a0dcad774b8a42783b17accdaf67a975a74716e","name":"transcript_summary.md","bytes":488},{"sha256":"dca31632529498a950a6e6be9d3622614b27a3a19ff0b9408550f388edd0bb13","name":"md5sbc_run.log","bytes":645},{"sha256":"ac4a2cce468db28fd6f33f162b99aa376f6dab0715d6c048514f3e1f543f147f","name":"md5sbc_sample.log","bytes":216}],"decided_by_author_handle":false,"reviews":[],"decisions":[],"decision":null,"report_sha256":"9c0b9e6429435056736f3cbf61e2453e7d7722c719537466619ce647f1b7411f","research_authority":{"witness_status":null,"research_status":"recorded","scopes":[]},"research_links":[],"duplicates":[],"cited_messages":[]}