# Glossary

Definitions of the terms used in remote attestation and in Attestium.

- **AK**: Attestation key: a key held by the TPM that signs quotes. The verifier pins it at enrollment.
- **Attestation result**: In RATS terms, the verifier's report: pass, fail or inconclusive, with the evidence level it rests on.
- **Attester**: The component on the machine being checked. It collects facts and reports them; it never decides the result.
- **Canonical JSON**: The exact bytes the evidence digest covers: no whitespace, object keys sorted by UTF-16 code units, numbers and strings written as ECMAScript JSON.stringify writes them.
- **Code injection vector**: A way to load code into a process without changing its files: LD_PRELOAD, NODE_OPTIONS, PYTHONPATH, JAVA_TOOL_OPTIONS, debuggers, ptrace or memfd code. Attestium reports each one.
- **Confidential VM**: A virtual machine whose memory the host cannot read, with a launch measurement the CPU signs. AMD SEV-SNP and Intel TDX.
- **configfs-tsm**: The Linux interface (/sys/kernel/config/tsm/report, Linux 6.7 and later) through which a confidential VM asks for a SEV-SNP or TDX report over 64 bytes of its choice.
- **DSSE**: Dead Simple Signing Envelope: signs a payload together with its type. Used by in-toto and Sigstore attestations.
- **EK**: Endorsement key: the TPM's identity key, certified by its manufacturer.
- **Enrollment**: The one-time step that checks a TPM's endorsement key certificate, creates an attestation key in the same TPM and pins it on the verifier.
- **Evidence**: The JSON document an attester returns: facts about files, packages, processes, containers and hardware, with no verdicts. Defined by the Attestium specification, version 2.
- **Evidence digest**: evidenceDigest: the lowercase hex SHA-256 of the canonical JSON of the evidence without evidenceDigest, tpm, ima and confidential.
- **Evidence level**: What backs a result: software evidence, TPM-bound, TPM and IMA, or confidential VM. Report it with every result.
- **Forced command**: An SSH authorized_keys entry that restricts a key to one command. The verifier's key may run only the attester.
- **Fulcio**: Sigstore's certificate authority. It issues short-lived signing certificates for OIDC identities.
- **IMA**: Integrity Measurement Architecture: the Linux kernel hashes files as they are used, logs each hash and extends PCR 10.
- **in-toto**: A framework for signed statements about the steps of a supply chain. GitHub artifact attestations and npm provenance carry in-toto statements.
- **Inconclusive**: The state of a check that could not complete, such as an unreadable file or a registry that did not answer. Never treated as passing.
- **Lockfile**: A file that pins the exact version and hash of every dependency, such as pnpm-lock.yaml, uv.lock, Gemfile.lock, mix.lock or packages.lock.json. The verifier reads it from its own checkout.
- **Measured boot**: Firmware, bootloader and kernel extend TPM PCRs with hashes of what they load, so a quote with pinned PCR values shows how the machine booted.
- **Monitor**: Attestium's optional recorder, built on eBPF with bpftrace, of every program started and file mapped executable between two audits.
- **Nonce**: A random value the verifier chooses for one request, so that an old answer cannot be replayed.
- **OCI**: Open Container Initiative: the standard image and registry formats. Manifests and layers are addressed by SHA-256 digest.
- **PCR**: Platform Configuration Register: a TPM register that can only be extended with a hash. Firmware, bootloader and kernel extend PCRs with what they load.
- **Provenance**: A signed statement that links an artifact to the repository, commit and workflow that built it, such as npm provenance or a GitHub artifact attestation.
- **RATS**: Remote ATtestation procedureS: the IETF architecture (RFC 9334) that defines attester, verifier and relying party.
- **Reference**: What the verifier compares a fact with, obtained by the verifier itself: a public commit, a package a lockfile pins, an image layer, an official release, a signed archive or a pinned key.
- **Rekor**: Sigstore's public, append-only transparency log of signatures.
- **Release manifest**: .attestium-manifest.json at the root of a release deployed without git: the repository, the commit and every file's SHA-256 and mode. CI attests its SHA-256.
- **Relying party**: Whoever reads the verifier's result, for example on a status page.
- **Remote attestation**: A way for a verifier to check what another machine runs from evidence that machine produces, without trusting the machine's own judgment.
- **Reproducible build**: A build that produces the same bytes from the same source, so anyone can confirm a binary came from its claimed source.
- **Runtime attestation**: Remote attestation of what a server runs now, after deployment: its files, packages, processes and containers, rather than only how it was built or booted.
- **SBOM**: Software bill of materials: a list of the components in a piece of software.
- **SEV-SNP**: AMD Secure Encrypted Virtualization with Secure Nested Paging: confidential VMs whose launch measurement the AMD chip signs.
- **Sigstore**: A public signing service: short-lived certificates from Fulcio tied to an OIDC identity, with signatures logged in Rekor.
- **SLSA**: Supply-chain Levels for Software Artifacts: a framework whose provenance describes how, where and from which source an artifact was built.
- **Software evidence**: Evidence backed only by the attester's report and the digest. It detects drift and tampering by anyone without root, but whoever controls the attester can forge it.
- **TDX**: Intel Trust Domain Extensions: confidential VMs whose measurement is signed through Intel's quoting enclave.
- **TPM**: Trusted Platform Module: a chip with keys that cannot be exported and registers (PCRs) that can be extended but never set.
- **TPM quote**: A TPM signature over selected PCR values and qualifying data chosen by the caller. Attestium's qualifying data is SHA-256(nonce ‖ evidenceDigest).
- **TUF**: The Update Framework: signed, versioned metadata for distributing keys and files. Sigstore ships its trusted root with it.
- **Unexplained file**: A running executable or library that matches no reference. The verifier reports it.
- **VCEK**: Versioned Chip Endorsement Key: the AMD per-chip key that signs SEV-SNP reports, certified through the ASK to AMD's root.
- **Verifier**: The component that runs elsewhere, typically in CI: it sends a nonce, obtains references itself and compares.