Certificate Transparency verifier

Trace a certificate into the public record.

Fetch the live certificate, decode SCT promises, rebuild the CT leaf, and verify the Merkle path against the log’s signed tree head.

TLS website certificate leaf + chain

SCT signed promise log id + timestamp

Leaf precert hash 00 || MerkleTreeLeaf

Path audit siblings left/right at each level

STH same root signed tree head

Ready to trace a certificate.

Handshake

Fetch the certificate

The trace starts the same way a browser does: open a TLS connection, receive the certificate chain, and inspect the leaf certificate for the domain name, issuer, validity window, and CT data.

How CT fits into Web PKI

The TLS leaf certificate will land here.

Baseline

Check normal validity

Certificate Transparency is not a replacement for normal TLS validation. The hostname still needs to match, and the chain still needs to lead back to a trusted root.

Web PKI background

Hostname and chain checks are separate from CT.

Promises

Read the SCT promises

A Signed Certificate Timestamp is a log’s signed promise that it will include a certificate or precertificate. Embedded SCTs usually point at a precertificate, so this tool rebuilds that CT leaf before asking the log for proof.

RFC 6962: Signed Certificate Timestamp

Signed Certificate Timestamps will appear as log cards.

Proof

Ask a log for Merkle proof

The log returns a short audit path instead of the whole tree. Combining the leaf hash with those sibling hashes should recreate the signed tree head root exactly.

Merkle audit paths Signed tree heads

Proof attempts will make the exact boundary visible.