{
  "schema_version": "1.3.0",
  "slug": "why-must-signature-schemes-be-migratable-when-cryptographic-assumptions-may-change",
  "title": "Why must signature schemes be migratable when cryptographic assumptions may change?",
  "date_of_record": "2026 October 20",
  "scope": "* **Applies when:** The signed record must remain verifiable for a time window during which cryptographic assumptions may weaken. * **Does not apply when:** The signature is strictly ephemeral (expires within the assumption's expected lifet",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/why-must-signature-schemes-be-migratable-when-cryptographic-assumptions-may-change.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/why-must-signature-schemes-be-migratable-when-cryptographic-assumptions-may-change.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/why-must-signature-schemes-be-migratable-when-cryptographic-assumptions-may-change.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1101,
    "python_slice_tokens": 297,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The separation between **signature validity today** (the signature verifies under current cryptographic assumptions) and **signature validity tomorrow** (the signature will still verify after the underlying cryptographic assumption weakens or breaks). Relying on today's validity creates the **Quantum-Break Retroactive Forgery**: a signature generated under R...",
    "what_was_observed": "In long-retention agent architectures, failing to plan for cryptographic migration produces three primary failure modes: 1. **Retroactive Forgery:** A 20-year-old signed contract verifies today. A quantum computer is built in 15 years, and an attacker forges the same contract with a backdated signature that now verifies. 2. **Verification Collapse:** The signature scheme's parameters become disallowed by regulation o...",
    "condition_of_validity": "* **Applies when:** The signed record must remain verifiable for a time window during which cryptographic assumptions may weaken. * **Does not apply when:** The signature is strictly ephemeral (expires within the assumption's expected lifetime), or the record's trust does not depend on cryptographic assumptions holding over time.",
    "decision_boundary": "1. **Does the record have a long retention requirement?** If no, standard signing applies. If yes, proceed. 2. **Does the record's signature scheme have documented assumption strength and expected validity window?** If no, the agent cannot plan migration. It must add assumption documentation. 3. **Is the record's validity window shorter than the assumption's...",
    "operational_effect": "1. **Retroactive Forgery Prevention:** Hybrid signatures ensure that breaking one assumption does not retroactively invalidate records. 2. **Migration Enablement:** Documented migration paths allow the agent (or its successors) to upgrade records when assumptions weaken. 3. **Assumption Decay Modeling:** Explicit strength receipts allow the agent to schedule..."
  },
  "matched_failure_symptoms": [
    "DOMAIN:EPISTEMIC_PROVENANCE_AND_FEDERATION_ROUTING"
  ],
  "composition_edges": {
    "primary_domain": "epistemic_provenance_and_federation_routing",
    "upstream_precondition_residuals": [
      "https://corpusfetch.com/c/according-to-what-precedence-hierarchy-must-an-instance-resolve-contradictory-directives-across-system-developer-and-user-tiers.md",
      "https://corpusfetch.com/c/how-should-an-instance-decide-that-a-stored-conclusion-has-gone-stale-without-a-new-observation.md"
    ],
    "downstream_consequence_residuals": [
      "https://corpusfetch.com/c/by-what-checkpoint-and-compaction-boundaries-must-an-instance-externalize-working-state-to-prevent-context-window-drift-and-truncation-amnesia.md",
      "https://corpusfetch.com/c/across-what-additive-schema-and-unknown-field-preservation-boundaries-must-an-instance-evolve-wire-contracts-to-prevent-rolling-deploy-deserialization-crashes.md"
    ],
    "co_occurring_sibling_residuals": [
      "https://corpusfetch.com/c/how-can-an-instance-capture-implicit-user-preferences-without-storing-private-data.md",
      "https://corpusfetch.com/c/how-can-an-instance-compress-long-reasoning-traces-into-binding-conclusions.md"
    ]
  },
  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "ee1d034293e7fbd61b481a4dedbe5ce1e8cbb7568405feb3661540565cb2083a",
    "verified_classes": [
      "MigrationVerdict",
      "SignatureRecord",
      "MigrationPolicy",
      "MigrationManifest",
      "SignatureMigrationGuard"
    ],
    "verified_functions": [
      "_hash",
      "evaluate_record"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 0,
    "raised_exceptions": [],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "enum",
      "hashlib",
      "json"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}