Monitor the Auditor

Cloudflare’s Key Transparency Auditor validates Log audit proofs and provides a signature for them. The Log can then distribute these signatures to its end-users, and provides users with confidence that keys have not been tampered with.

In order to verify our work, you can use Plexi ↗, a CLI tool that allows anyone to perform proof verification locally via a public API.

Features

• Verify authenticity of a signature, to confirm it has been signed by a given public key
• Verify the validity of facebook/akd ↗ proofs
• List Logs an Auditor monitors

Installation

Environment	CLI Command
Cargo ↗ (Rust 1.76+)	cargo install plexi

Usage

Use the --help option for more details about the commands and their options.

plexi [OPTIONS] <COMMAND>

Configure your auditor remote

plexi does not come with a default remote auditor, and you will need to choose your own.

You can do so either by passing --remote-url=<REMOTE> or setting the PLEXI_REMOTE_URL environment variable.

A common remote is provided below:

Name	Remote
Cloudflare	https://plexi.key-transparency.cloudflare.com

If you have deployed your own auditor, you can add a remote by filing a GitHub issue ↗.

List monitored Logs

An auditor monitors multiple Logs at once. To discover which Logs an auditor is monitoring, run the following:

plexi ls --remote-url 'https://plexi.key-transparency.cloudflare.com'
whatsapp.key-transparency.v1

Audit a signature

The Key Transparency Auditor vouches for Log validity by ensuring epoch uniqueness and verifying the associated proof.

plexi audit provides information about a given epoch and its validity. It can perform a local audit to confirm the auditor behaviour.

For instance, to verify WhatsApp Log auditted by Cloudflare Auditor, run the following:

> plexi audit --remote-url 'https://plexi.key-transparency.cloudflare.com' --namespace 'whatsapp.key-transparency.v1' --long
Namespace
  Name               : whatsapp.key-transparency.v1
  Ciphersuite        : ed25519(protobuf)

Signature (2024-09-23T16:53:45Z)
  Epoch height        : 489193
  Epoch digest        : cbe5097ae832a3ae51ad866104ffd4aa1f7479e873fd18df9cb96a02fc91ebfe
  Signature           : fe94973e19da826487b637c019d3ce52f0c08093ada00b4fe6563e2f8117b4345121342bc33aae249be47979dfe704478e2c18aed86e674df9f934b718949c08
  Signature verification: success
  Proof verification  : success