in-toto

A framework that verifies every step of a software supply chain was carried out as planned, by authorized parties, on un-tampered artifacts.

Category: Supply Chain
CNCF maturity: Graduated
Language: Python (>=3.9)
License: Apache-2.0
Repository: in-toto/in-toto
Documented at commit: a8ce9ee (2026-05-19)

What it is

in-toto protects the integrity of a software supply chain end to end. A project owner writes a signed layout that lists the steps of the chain (tag, build, test, package) and the functionaries authorized to perform each one. When a functionary runs a step, in-toto records what command ran and which files went in and came out into a signed link file. At release time the layout, the links, and the owner's public keys travel with the product, and in-toto-verify checks that the recorded chain matches the planned one (in_toto/in_toto_verify.py:222).

The Python repository documented here is the reference implementation of the in-toto specification. It ships six command line tools (pyproject.toml:50). The specification itself, and ports in Go, Java, and Rust, live in sibling repositories under the same project.

in-toto is a format and a verification model, not a hosted service. It sits below opinionated layers like SLSA (which expresses build provenance as an in-toto attestation) and alongside Sigstore (which solves the signing and transparency problem).

When to use it

You need cryptographic proof that a released artifact came from the exact sequence of build steps you defined, with no unauthorized step inserted.
You want to bind separate CI stages (source, build, package) to specific signing keys and enforce that the output of one stage is the input of the next.
You are producing or consuming SLSA provenance and want the underlying envelope and verification logic.
It is a poor fit when you only need to sign a single artifact with no notion of a multi-step chain: a plain Sigstore or GPG signature is simpler.
It does not manage key distribution or revocation; pair it with TUF or Sigstore for that.

In this deep-dive

History: origin, milestones, and why it exists.
Architecture: components and how requests flow.
Adoption & Ecosystem: who runs it and what surrounds it.
Internals: the code paths that matter, read from source.
Getting Started: install and a first working setup.

in-toto ​

What it is ​

When to use it ​

In this deep-dive ​

Sources ​

in-toto

What it is

When to use it

In this deep-dive

Sources