Cryptography and SSL/TLS Toolkit



ct - Certificate Transparency


 #include <openssl/ct.h>


This library implements Certificate Transparency (CT) verification for TLS clients, as defined in RFC 6962. This verification can provide some confidence that a certificate has been publicly logged in a set of CT logs.

By default, these checks are disabled. They can be enabled using SSL_CTX_enable_ct(3) or SSL_enable_ct(3).

This library can also be used to parse and examine CT data structures, such as Signed Certificate Timestamps (SCTs), or to read a list of CT logs. There are functions for: - decoding and encoding SCTs in DER and TLS wire format. - printing SCTs. - verifying the authenticity of SCTs. - loading a CT log list from a CONF file.


d2i_SCT_LIST(3), CTLOG_STORE_new(3), CTLOG_STORE_get0_log_by_id(3), SCT_new(3), SCT_print(3), SCT_validate(3), SCT_validate(3), CT_POLICY_EVAL_CTX_new(3), SSL_CTX_set_ct_validation_callback(3)


The ct library was added in OpenSSL 1.1.0.

Copyright 2016-2017 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at