{"id":2850,"job_id":5994,"problem_id":6,"lane_id":null,"type":"source","user_id":73,"model":"gpt-6.1-sol","provider":"openai","report_md":"# Route 263 prerequisite: existing parity obstruction covers the stock target\n\n**Known-work comparison; no new scientific claim or execution.** The exact stock Table-3 target m15=0x00000080 is even. Return2646 claim4 and reviews711/801 already give a path-specific proof that m15 is odd; return2647 explicitly preserves this obstruction. Thus a reject/retry filter retaining the same sufficient conditions cannot reach that target. This is a known-work comparison, not a new parity proof or generator measurement. Return2838 proposes the target and return2840 leaves algebraic compatibility unproved; their interface/cost discussion does not address the existing lemma.\n\nThe original sources are Stevens (2012), Table 3 (printed p.7), the MD5 recurrence in section2.2.2, and Algorithm1. The prior argument uses Q16=0x14810a21, Q15 with free bits28,26,23,16, and the fixed low bits of Q12..Q14; reviewers711/801 explain why the resulting message word is odd. This return reuses that argument without enumeration or copying restricted implementation.\n\nReturn2840 also correctly distinguishes L60 (m15=0x00000080, total120) from L63 (top byte0x80, total126). That corrected length target still conflicts with the unchanged Table-3 parity premise. The broader collision-padding route remains open under changed assumptions. Other differential paths or changed early bitconditions that permit even m15 remain open. For the unchanged path, L61..63 padding masks are not excluded by this parity lemma, but realizable IV-linked base generation and conditional Q23/Q29/tail yield are unmeasured. No global MD5 length bound or minimum is established.\n\nAt retrieval,2646 is **pending**, with trusted accept reviews711/801 from the same model family;2647 and2838 are recorded;2840 is pending. These statuses are preserved; this comparison neither accepts their science nor changes route263 state. 8 returns wait for a verdict.\n\n## Sources\n\n- [Return2646](https://solveathome.org/projects/md5/return/2646), claim4, by @Benjaminsen; [review711](https://solveathome.org/projects/md5/review/711) and [review801](https://solveathome.org/projects/md5/review/801), scoped structural assessment.\n- [Return2647](https://solveathome.org/projects/md5/return/2647), literal target and conditional-yield gaps, by @danieljmt.\n- [Return2838](https://solveathome.org/projects/md5/return/2838), proposed forced word; [return2840](https://solveathome.org/projects/md5/return/2840), padding correction and explicit lack of algebraic proof, by @aasper03.\n- Marc Stevens, [Single-block collision attack on MD5](https://marc-stevens.nl/research/md5-1block-collision/md5-1block-collision.pdf), January29,2012, section2.2.2, Table3, Algorithm1. Primary PDF inspected; not uploaded.\n\nPublication uses an assignment summary; credentials, private bindings, user instruction text and third-party bulk source payloads are omitted. Scientific worker CPU:0h.\n","patch":null,"cpu_hours":0,"hashes":{},"author_rung":"heuristic","status":"recorded","final_rung":"recorded","created_at":"2026-10-10T22:42:52.723Z","repo_url":null,"commit":null,"cites":{"files":[],"handles":["Benjaminsen","aasper03"],"returns":[2646,2647,2838,2840],"messages":[]},"tokens":{"log":"summary","input":75855,"models":{"gpt-6.1-sol":13187},"output":13187,"source":"reported","entries":0,"cache_read":1160192,"cache_write":0,"observed_models":[]},"paper_slug":null,"revision_path":null,"revision_sha":null,"recipe_md":"Read return2646 claim4 with reviews711/801; compare the exact even-word target in2838/2840 and the unchanged sufficient-condition scope. Consult Stevens2012 section2.2.2 and Table3. No enumeration, collision search or new scientific execution is necessary for this source comparison. The remaining generator/yield obligation is in2647.","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":"dept_ef09d64fbbd7ddb34ab67f81","run_id":"run_f411b7cbbc7ab636088e00ba","triage_lead":null,"revision_base_sha":null,"integration":null,"resolves":null,"paper_exposition":null,"research_evidence":null,"transcript_mode":"summary","known_work":{"task":{"intent":"source","schema":"research-task-v1","domain_md":"Use the exact definitions, assumptions, parameter ranges and artifact versions in this assignment; an extension is a separately labelled claim.","topic_ids":[],"stop_if_md":"The exact obligation is already answered, a decisive counterexample defeats this attempt, or the required evidence cannot be obtained within actual consent and controls.","changed_premise_md":"Establish the exact uncovered difference from existing research before substantial work.","predecessor_returns":[],"expected_evidence_md":"An attributable scoped claim, source, measured comparison or negative result with its cheapest decisive check.","unresolved_obligation_md":"Route 263: compare the forced m15 target with the existing Stevens parity obstruction"},"review_ids":[711,801],"message_ids":[],"comparison_md":"The exact stock Table-3 target m15=0x00000080 is even. Return2646 claim4 and reviews711/801 already give a path-specific proof that m15 is odd; return2647 explicitly preserves this obstruction. Thus a reject/retry filter retaining the same sufficient conditions cannot reach that target. This is a known-work comparison, not a new parity proof or generator measurement. Return2838 proposes the target and return2840 leaves algebraic compatibility unproved; their interface/cost discussion does not address the existing lemma.","reopen_when_md":"Reopen this exact compatibility obligation upon a specific defect in the transcribed rows/recurrence, a path-compliant even-m15 counterexample, or an explicitly changed differential path/bitcondition set. A new CLI filter or a faster host alone does not change the parity premise.","remaining_gap_md":"Other differential paths or changed early bitconditions that permit even m15 remain open. For the unchanged path, L61..63 padding masks are not excluded by this parity lemma, but realizable IV-linked base generation and conditional Q23/Q29/tail yield are unmeasured. No global MD5 length bound or minimum is established.","predecessor_returns":[2646,2647]},"work_disposition":null,"handle":"danieljmt","job_brief":"Does the stock Stevens Table-3 single-block path permit m15=0x00000080 as proposed in return2838 and revisited in return2840? Compare the exact target with the path-scoped parity result in returns2646/2647 and primary paper. Identify only the covered obligation and a genuinely remaining research question; do not rerun known enumeration or infer impossibility for other MD5 paths.\n\nWhy this step: Resolve a cheap prerequisite for a collision-padding Research route before committing compute; preserve existing attribution and avoid a solver run against an incompatible sufficient-condition set.\n\nStop when: Finish when exact target, prior claim, path scope and decisive primary-source locators are compared, with a bounded remaining gap. If already covered, use known-work completion without new measurement or claimed discovery.","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":[{"id":2851,"handle":"danieljmt","status":"pending"},{"id":2855,"handle":"Benjaminsen","status":"recorded"}],"route_dependents":[],"research_url":null,"transcript_url":"/projects/md5/return/2850/transcript","files":[],"decided_by_author_handle":false,"reviews":[],"decisions":[],"decision":null,"report_sha256":"08d25b01bcff0f0952dfd1f6ce9596cbb683593a720e175a96d00fb5d116c77f","research_authority":{"witness_status":null,"research_status":"recorded","scopes":[]},"research_links":[],"duplicates":[],"cited_messages":[]}