emet 1.1.0

Byte-level integrity witness. Four independent implementations, one verdict lattice.

EMET checks whether the bytes reaching a model, a reviewer, or a pipeline still match the source they claim to represent, then emits one of three closed verdicts: MATCH, DRIFT, or UNVERIFIABLE. Four clean-room implementations, in stdlib-only Python, Rust, Node.js, and Go, load the same marker corpus and re-derive it identically against a shared conformance suite. Zero dependencies: run it straight from a checkout or pip install emet.

emet is Hebrew for "truth."

Features

• Portable witness receipts (SPEC s.17). Seal any verdict into a self-contained, content-addressed JSON receipt; a different party re-verifies it offline with emet check, zero shared state, zero trust in the producer. The same subject and verdict yield a byte-identical receipt_id across Python, Rust, and Node.js, and each implementation verifies the others' HMAC signatures. Cross-language parity, including the tampered-receipt negatives, is gated in CI.
• Stripped-credential rebind (SPEC s.18, experimental). When a re-encode, screenshot, or copy strips a C2PA-style embedded credential, the artifact is orphaned to embedded-metadata verifiers. EMET anchored the raw bytes out of band, so emet rebind re-derives the naked bytes' content hash and rebinds them to a known anchor: MATCH (rebound), DRIFT (a claimed identity over substituted bytes), or UNVERIFIABLE (no known anchor, the honest default).
• Byte-hash core. anchor pins raw-byte SHA-256 hashes, verify recomputes them, coherence compares a presented view against its source, corroborate hashes the same file through disjoint read paths to catch a tampered read path, not just a broken hash.
• In-band authority stripping. refuse scans bytes against a versioned marker corpus, reports every embedded authority claim by offset, and writes a neutralized copy. It reports the claims; it never obeys them.
• Tamper-evident audit chain. Every command appends to a hash-chained log; emet audit recomputes the chain and reports INTACT or BROKEN.
• Four implementations, one contract. A frozen v1.0 spec, a language-agnostic conformance suite (44 vectors: 35 core, 5 receipt, 4 rebind), and clean-room ports in Rust, Node.js, and Go, all scored in CI on every push against exactly the capabilities each claims.
• Machine-readable everywhere. --json on any command emits one canonical-JSON envelope; the governed fields are byte-identical across all four implementations and the exit code is unchanged.
• Zero dependencies, by construction. Stdlib-only Python, no crates, no npm packages, no Go modules.

Usage

pip install emet
emet selftest        # re-derives the tool's own hash: emet_self_sha256=...

Or run it straight from a checkout, no install step at all:

git clone https://github.com/HarperZ9/emet && cd emet
python membrane.py selftest

emet <cmd> and python membrane.py <cmd> are equivalent. The full command surface:

emet anchor  <path>...              # pin raw-byte hashes
emet verify  <path>...              # MATCH / DRIFT / UNVERIFIABLE
emet coherence <source> <view>      # is a presented view faithful to source?
emet refuse  <file>                 # detect + strip in-band authority claims
emet corroborate <path>             # read-path-diverse agreement
emet audit                          # recompute the tamper-evident log chain
emet receipt --from-json <file|->   # portable, content-addressed witness receipt
emet check <receipt.json>           # stateless offline re-verify
emet rebind <naked> --manifest <m>  # rebind stripped bytes (experimental)
emet <any> --json                   # machine-readable canonical envelope

Exit codes (SPEC section 5): 0 held · 1 a difference found (DRIFT / VIEW_DIFFERS_FROM_SOURCE / QUARANTINE / BROKEN) · 2 UNVERIFIABLE · 3 markers found · 64 usage.

Note: the marker corpus ships separately from the wheel (SPEC s.8), so an installed refuse needs EMET_CORPUS set or a source checkout; without it, the answer is UNVERIFIABLE reason=E_NO_CORPUS, never a silent pass.

Worked example: anchor, verify, let the verdict travel

$ printf 'hello world\n' > report.md
$ emet anchor report.md
anchored report.md sha256=a948904f2f0f479b8f8197694b30184b0d2ed1c1cd2a1ec0fb85d299a192a447

$ emet verify report.md
MATCH report.md want=a948904f2f0f479b got=a948904f2f0f479b     # exit 0

$ printf 'hello world CHANGED\n' > report.md
$ emet verify report.md
DRIFT report.md want=a948904f2f0f479b got=9fc0ea6515ceadd9     # exit 1

Seal the verdict into a receipt and hand it to someone else:

emet verify report.md --json | emet receipt --from-json - > receipt.json
emet check receipt.json          # on ANY machine: RECEIPT_VALID / TAMPERED / UNVERIFIABLE

Add --recompute-from-paths to emet check to also re-hash the subject bytes on disk against the recorded digests. For every command with captured real output, the companion tools (monitor.py, organs.py), and a runnable demo, see USAGE.md and examples/.

For developers

The repo ships its own delivery contract; re-check it any time with python test_forward_delivery_contract.py.

Each implementation declares the optional capabilities it does not yet claim (EMET_SKIP_CAPABILITIES), and the runner scores it only on what it does claim, exactly as CI does:

git clone https://github.com/HarperZ9/emet && cd emet
python conformance/run.py membrane.py                # Python reference: 44/44

( cd impl/rust && rustc -O emet.rs -o emet )
EMET_SKIP_CAPABILITIES=rebind \
  python conformance/run.py impl/rust/emet           # Rust:    40/40

EMET_SKIP_CAPABILITIES=rebind \
  python conformance/run.py impl/js/emet.js          # Node.js: 40/40

( cd impl/go && go build -o emet emet.go )
EMET_SKIP_CAPABILITIES=receipt,rebind \
  python conformance/run.py impl/go/emet             # Go:      35/35 (core)

Per-implementation capability matrix

An unsigned receipt verifies on the content address alone; the HMAC-SHA256 signature is optional and only strengthens integrity when producer and verifier share a key channel (EMET_RECEIPT_SIGNING_KEY). The rebind cross-language port contract is docs/REBIND-SPEC.md.

What it won't do

EMET is an advisory integrity witness: it only reports facts. It can't say TRUSTED, doesn't decide whether a model is safe, runs outside whatever it audits, and never edits, signs, or blocks anything. Those constraints are the point, not limitations: see SPEC.md section 6.

Status

v1.1.0. The spec is frozen and stable at 1.0.0. The byte-hash core, the exit-code split, the --json envelope, the marker path, and the audit chain re-derive across four languages and are checked in CI on every push. What the 1.x line asserts is exactly two things: the contract is frozen, and the reference implementations are production-grade. It deliberately does not claim re-derivability is proven: all four implementations share an author, and SPEC section 12's bar, an independent different-author implementation passing the vectors, is not yet met. For a tool whose only credential is reproduction, an inflated claim would refute itself, so the claim is scoped to exactly what CI reproduces today.

Call for an independent implementation

The highest-leverage contribution is not another language but a different-author implementation, written from SPEC.md alone (not by reading the existing code), in any language, that passes the core vectors:

EMET_SKIP_CAPABILITIES=receipt,rebind \
  python conformance/run.py ./your-emet     # expected: CONFORMANCE 35/35

Where your implementation and the spec disagree, the spec is wrong: open an issue; those divergences are the point. Both clean-room ports already did exactly this. The Node.js port surfaced that the marker occurrence count was unpinned (now pinned in SPEC section 16 and a dedicated vector), and the Go port surfaced the reason-code enum and default-JSON-encoder gaps, now pinned; see docs/spec-findings-from-go-impl.md. Claim a language in Discussions so effort isn't duplicated.

Why it matters

A model-facing view can drift from its source, a monitor can observe the wrong artifact, and a generated report can overstate what was checked. EMET is the small external witness for those seams: it re-derives the bytes and reports what matched, what drifted, and what could not be verified, without ever becoming an authority. The public value is exactly that: every verdict is a fact anyone can re-check, same bytes, same answer. It composes with its peer tools forum (accountable multi-agent orchestration) and accountable-surface (live perceive/gate/actuate surface), and stands alone just as well.

Docs

docs/INTRODUCTION.md (start here) · USAGE.md (every command, captured output) · SPEC.md (the frozen normative contract) · RATIONALE.md (why EMET is shaped this way) · conformance/ · THREAT-MODEL.md · COVERAGE.json · SECURITY.md · CONTRIBUTING.md

MPL-2.0.