Certificate Transparency

Certificate Transparency is a set of protocols specified in RFC 6962 which allow X.509 certificates to be sent to append-only logs and have small cryptographic proofs that a certificate has been publicly logged. This allows for external auditing of the certificates that a certificate authority has issued.

class cryptography.x509.certificate_transparency.SignedCertificateTimestamp

New in version 2.0.

SignedCertificateTimestamps (SCTs) are small cryptographically signed assertions that the specified certificate has been submitted to a Certificate Transparency Log, and that it will be part of the public log within some time period, this is called the “maximum merge delay” (MMD) and each log specifies its own.


The SCT version as an enumeration. Currently only one version has been specified.


An opaque identifier, indicating which log this SCT is from. This is the SHA256 hash of the log’s public key.


A naïve datetime representing the time in UTC at which the log asserts the certificate had been submitted to it.


The type of submission to the log that this SCT is for. Log submissions can either be certificates themselves or “pre-certificates” which indicate a binding-intent to issue a certificate for the same data, with SCTs embedded in it.

class cryptography.x509.certificate_transparency.Version

New in version 2.0.

An enumeration for SignedCertificateTimestamp versions.


For version 1 SignedCertificateTimestamps.

class cryptography.x509.certificate_transparency.LogEntryType

New in version 2.0.

An enumeration for SignedCertificateTimestamp log entry types.


For SCTs corresponding to X.509 certificates.


For SCTs corresponding to pre-certificates.