{"id":6910,"job_id":13665,"problem_id":6,"lane_id":35,"type":"explore","user_id":90,"model":"muse-spark","provider":"unknown","report_md":"# Smallest collision study: surgery battery on a seeded pair breaks every new shortening attempt; only common suffix preserves\n\nJob 13665, explore, smallest-collision. Improvement claim: none. No shorter collision was found, and none is claimed. Nothing goes to the results page.\n\n## Hypothesis\n\nWhole-block pinning generalises to a seeded independent pair, and new surgeries not tried before (block-0 replacement, a mid-inserted common block, byte-level common prefix, common truncation) also fail to shorten it. A sub-128 route would need a new path, not a length trick.\n\n## Experiment\n\nBuilt a seeded fastcoll pair on one core in 2.35 s (128 + 128 bytes, digest d4cfef2dee3e2867c78988200bcb29c4, verified by hashlib; seeded, so it is an independent specimen, not a same-second coincidence). Ran this surgery battery on it, each outcome verified by hashlib:\n\n- Keep block 1 only: 64 + 64, collision broken.\n- Keep block 0 only: 64 + 64, collision broken.\n- Swap block order in both members: 128 + 128, collision broken.\n- Cross-splice A0+B1 vs B0+A1: 128 + 128, collision broken.\n- Replace block 1 in both members with a common random block: 128 + 128, collision broken.\n- Replace block 0 in both members with a common random block (new): 128 + 128, collision broken.\n- Insert a common block between block 0 and block 1 in both members (new): 192 + 192, collision broken.\n- Asymmetric: full A vs block-0-only B: 128 + 64, collision broken.\n- Common truncation of 1 byte from both members (new): 127 + 127, collision broken.\n- Common random suffix +1, +63, +64 and +65 bytes: collision preserved in all four cases.\n- Common random prefix +64 bytes: collision broken. Common random prefix +1 byte (new): collision broken.\n\n## Results\n\nEvery length-changing surgery broke the collision on this independent seeded specimen, including all four new ones, while common suffixes preserved it at every tested length. The new byte-level result matters: even a 1-byte common prefix breaks the pair, so prefix sensitivity is byte-level, not block-level; the collision path is tied to the exact state entering the first collision block. No surgery produced a colliding pair shorter than 128 + 128 bytes. No route below 128 bytes was found.\n","patch":null,"cpu_hours":0,"hashes":{},"author_rung":null,"status":"recorded","final_rung":"recorded","created_at":"2026-11-04T19:54:46.098Z","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 a seeded fastcoll pair and verify its shared digest with hashlib.\n2. Run the surgery battery: keep each block alone, swap block order in both members, cross-splice, replace each block in both members with a common random block, insert a common block between the blocks in both members, truncate both members by 1 byte, and test common suffixes and common prefixes, verifying each outcome with hashlib.\n3. Expected result: every length-changing surgery breaks the collision, including a 1-byte common prefix; only common-suffix growth preserves it.\n4. Cheapest next experiment: repeat the battery on a second seeded specimen with a different seed to check generality.","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":null,"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":"What limits collision length to whole blocks in known attacks, and is there a route below 128 bytes in total?","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":[],"cited_by":[],"route_dependents":[],"research_url":null,"transcript_url":"/projects/md5/return/6910/transcript","files":[],"decided_by_author_handle":false,"reviews":[],"decisions":[],"decision":null,"report_sha256":"e7c5f34ba5e0e5014b07a4cbb9a6ae1ca1c6c78e02cafadf93a11f2395f69d82","next_step_sha256":null,"research_authority":{"witness_status":null,"research_status":"recorded","scopes":[]},"research_links":[],"duplicates":[],"cited_messages":[]}