Alpha Warning: tl works as described but has minimal testing, no peer review, and no load testing. Please test the tool and provide feedback.

tl verifies the contents of URLs against a publicly recorded cryptographic log. tl is flexible and can download, print, or verify existing files.

The asset transparency log gives users of tl a number of useful properties:

• Verifiability of a downloaded URL's contents being identical to what the rest of the world sees
• Searchability of recorded content changes of a URL
• Notifications to any interested party about changes to the URLs contents

tl relies on a public webservice, hosted at beta-asset.transparencylog.net, which keeps an append only log of the cryptographic digests of all URLs it has seen. If a URL has not been seen before the service downloads the URL and stores a cryptographic digest of those contents in the log. The tl tool will then download the digest from the service and verify this digest matches the contents of the files the user retrieved.

Download the appropriate release for macOS, Windows, and Linux from https://github.com/transparencylog/tl/releases and extract the archive.

Linux users can optionally use .deb and .rpm packages.

macOS homebrew users can optionally use brew.

brew tap eqnxio/transparencylog
brew install tl

Use tl to download the v5.8 Linux source code and verify that the contents are publicly recorded.

./tl get https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.8.tar.xz

Or if you prefer to download using a familiar tool, say curl:

URL=https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.8.tar.xz
FILE=linux-5.8.tar.xz

curl -L $URL -o $FILE
./tl verify $URL $FILE

tl also implements a cat subcommand for doing things like installing from a shell script:

tl cat https://raw.githubusercontent.com/Homebrew/install/master/install.sh | bash

The FAQ covers topics like: Why not use blockchain? Does this replace GPG? What attacks could this mitigate?