CT(7ossl)

💖 NAME 💖

ct — Certificate Transparency, bestie!! (this is the ct(7ossl) page, and yes she's a whole library) 🎀

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✨ SYNOPSIS ✨

#include <openssl/ct.h>

that's literally it, that's the whole synopsis, we love a low-effort queen 👑

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🦋 DESCRIPTION 🦋

okay so. this library implements Certificate Transparency (CT) verification for TLS clients, exactly as defined in RFC 6962. and what that actually does for you is give you some confidence that a certificate has been publicly logged in a set of CT logs. like, the internet is keeping receipts. iconic behavior honestly 💅

so by default? these checks are disabled. turned off. not doing anything. 😴 you gotta enable them yourself with SSL_CTX_enable_ct(3) or SSL_enable_ct(3). do it. slay.

but wait, there's more — this library can also be used to parse and examine CT data structures, like Signed Certificate Timestamps (SCTs), or to read a list of CT logs. main character energy for data structures fr fr 🔥

the functions she offers are:

• 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 🍓

ngl that's a full little toolkit and it ate 💀✨

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🌈 SEE ALSO 🌈

• 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)

and yes SCT_validate(3) is in there twice 😭 the original page lists it twice and we are nothing if not faithful — she said "double it and give it to the next person" 🫶

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🌸 HISTORY 🌸

the ct library was added in OpenSSL 1.1.0. a vintage. a classic. we stan an OG 🎀

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💜 COPYRIGHT 💜

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 <https://www.openssl.org/source/license.html>.

ok bestie read the license, it's giving legally required and we don't play about that 💀

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⭐ and that's the whole page!! brought to you by OpenSSL 3.5.6, dated 2026-04-07 — mwah, go verify some certificates, ily 💖🦋✨