Logsiegel

Prove your AI didn't lie.

Website · Try the browser verifier (offline, drag & drop a receipt) · PyPI

Tamper-evident, privacy-preserving event logs for AI systems.

When an AI system or agent acts — answers, decides, books, escalates — the record of what happened usually lives in an ordinary database at the operator: silently editable, verifiable by no one. Logsiegel records AI lifecycle events (inference, model changes, human overrides, …) into an append-only log with hash chaining and Ed25519-signed Merkle checkpoints — the same battle-tested construction as Certificate Transparency (RFC 6962). Observability tools show what happened; Logsiegel makes it provable: offline, by any third party holding a checkpoint or a single-entry receipt, without access to the operator's infrastructure. Deliberately no blockchain: no consensus, no tokens, no GDPR conflict.

Where this matters: accountability for autonomous agents (what did the agent do, when, on whose behalf?) and record-keeping duties such as the EU AI Act's automatic logging and retention rules (Art. 12/19) — built for teams that don't have a compliance-engineering department.

Why

• Logs in ordinary databases are silently editable. When an AI decision is challenged, "our logs say X" proves nothing. Logsiegel makes any after-the-fact modification, reordering or truncation cryptographically detectable.
• Single-entry receipts. An affected person or auditor gets one entry plus an RFC 6962 inclusion proof and a signed checkpoint — verifiable offline with the log's public key alone, no access to the full log.
• Privacy by design. Only event metadata and salted payload hashes enter the log. Raw prompts/outputs are stored separately, encrypted per entry; a pluggable PII detector masks identifiers in stored payloads. Deleting the per-entry key (crypto-shredding) removes the content and the hash linkability, while the log stays byte-identical and verifiable — deletion rights and tamper-evidence stop being a contradiction.
• Speaks the ecosystem's language. Event attributes follow the OpenTelemetry GenAI semantic conventions; adapters hook into existing stacks (LiteLLM today, OTel collector and agent-framework adapters planned) instead of asking you to re-instrument.

Quick start

pip install logsiegel            # from source: pip install -e ".[dev]"
pip install "logsiegel[saklam]"  # optional: in-process PII masking of stored payloads (Saklam licence key required)

logsiegel init ./mylog --origin "acme.example/support-bot"
logsiegel log ./mylog --event inference \
  --attr gen_ai.request.model=gpt-5 --attr gen_ai.usage.input_tokens=412 \
  --input "customer question …" --output "answer …" --store-payload
logsiegel checkpoint ./mylog
logsiegel verify ./mylog                    # PASS: chain + Merkle roots + signatures
logsiegel receipt ./mylog --seq 1 --out receipt.json
logsiegel verify-receipt receipt.json \
  --pubkey mylog/keys/signing_key.pub       # single entry, offline, no log access
logsiegel export ./mylog                    # auditor-readable dossier (markdown)
logsiegel shred ./mylog --seq 1             # GDPR erasure; verify still passes

Full walkthrough incl. receipts and tamper detection: python examples/demo.py (PII masking: python examples/pii_demo.py)

LiteLLM integration

import litellm
from logsiegel.integrations.litellm_logger import LogsiegelLogger

litellm.callbacks = [LogsiegelLogger("/var/lib/logsiegel/prod", store_payload=True)]

Every completion becomes a signed-committable inference event; failures are recorded as anomaly.

How verification works

1. Each entry embeds the SHA-256 of its predecessor (hash chain); appends are serialized under an exclusive file lock and fsynced before they are acknowledged.
2. checkpoint commits to an RFC-6962 Merkle root over the first N entries and signs {origin, size, root, ts} with Ed25519.
3. verify recomputes everything from the raw files: broken chains, edited entries, shrunken logs and forged checkpoints all fail loudly.
4. receipt / verify-receipt prove a single entry against a signed checkpoint via an inclusion proof; consistency proofs (append-only growth between two checkpoints, the check a witness performs) ship in logsiegel.merkle.

Threat model, honestly

Logsiegel is tamper-evident, not tamper-proof. Precisely:

• Against third parties and after-the-fact edits: any modification, reordering or truncation of committed entries breaks verification against every previously distributed checkpoint or receipt.
• Against the operator: the operator holds the signing key and could rewrite and re-sign the entire log. That is detectable exactly when someone else holds an earlier checkpoint or receipt — so distribute them (to auditors, counterparties, or an independent witness co-signing checkpoints; witness support is on the roadmap). Verify against an out-of-band copy of the public key (logsiegel verify --pubkey …), not the copy stored next to the log.
• Completeness is not a cryptographic property. The log proves that recorded events are unaltered — never that everything was recorded. Closing that gap is an integration property: log at a choke point that actions must pass through.
• Timestamps are the operator's claims until checkpoints are co-signed by an external witness.

Status

v0.1.2 on PyPI (packaging metadata only — see CHANGELOG.md). v0.1.1 added the optional saklam extra: in-process PII masking of stored payloads via the Saklam engine, no HTTP hop, licence key required. v0.1.0: local filesystem, minimal AI-lifecycle event taxonomy (pluggable per writer), RFC 6962 inclusion + consistency proofs, single-entry receipts, crypto-shredding, PII masking, dossier export, LiteLLM adapter, and an independent browser verifier (plain JS + WebCrypto, single HTML file, runs offline; source in verifier/, live at logsiegel.com/verifier) that agrees with the Python reference on every test vector. 57 tests.

Roadmap: agent-action taxonomy (tool calls, delegation, value flows, human intervention) with OTel GenAI span semantics, mandate binding to verifiable credentials / eID ecosystems, independent witness co-signing (C2SP-style checkpoints), retention policy engine, TypeScript SDK, mapping to emerging logging standards (EU AI Act Art. 12, prEN 18229-1, ISO/IEC 24970).

Maintainers

Stefan Böck (code) and Emmanuelle St-Pierre-Wittwer (regulatory). Project site: logsiegel.com · contact: logsiegel@stefan.boeck.name · security reports: SECURITY.md

License

Apache-2.0