Auditor-Assisted Summary-Channel Verification for Hosted LLM Identity Substitution

Summary

SUMMARK is an auditor-assisted watermarking framework that verifies whether a hosted LLM served a claimed identity, using user-visible reasoning summaries as a keyed audit surface. Auditors enroll identities and calibrate per-identity thresholds before deployment, and audits rely only on the released output. Across model families, scales and task domains, the method reliably detects cross-family and cross-scale substitutions at low false-positive rates while preserving answer quality, though the authors also report failure boundaries under rewriting stress tests and text-only spoofing.

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