Sigsum logging brings transparency to signed checksums. This makes it possible to detect malicious and unintended key-usage. In other words, no signature accepted by an end-user goes unnoticed.

A new signature made with my key was just logged. Was that signature expected?

Specific use-cases can be implemented on-top of the minimal building block that Sigsum provides. Examples include transparency for executable binaries, TPM quotes, and onion address rulesets.

Everyone gets the same binaries. Signed binary checksums become public in Sigsum logs. Each binary is locatable on a separate release page. An independent monitor can verify these claims.

Sigsum is designed to be secure against a powerful attacker that controls:

• The signer’s secret key and infrastructure
• The log’s secret key and infrastructure
• A threshold of so-called witnesses that cosign the log

Any use-case that cannot tolerate a few minutes of logging latency is out of scope. This and other aspects keep the Sigsum design simple, both with regards to operations and end-user verification.