CT(7ossl)

💜 CT(7ossl) — like, the Certificate Transparency page, bestie

okay so real quick: this is the ct page from the OpenSSL manual set, and it's genuinely one of the more underrated ones. buckle up 🎀

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✨ NAME ✨

ct — Certificate Transparency. that's it, that's the vibe. 🦋

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🌸 SYNOPSIS 🌸

#include <openssl/ct.h>

that's the whole synopsis. one include. she's low maintenance and we respect that 💅

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👑 DESCRIPTION 👑

okay so bestie, this library implements Certificate Transparency (CT) verification for TLS clients, exactly as defined in RFC 6962. and what does that actually do for you? it can give you some confidence that a certificate has been publicly logged in a set of CT logs. that's the whole point — public logging means you can catch shenanigans. no cap. 🔥

heads up though: by default, these checks are disabled. 😭 they don't just turn on for you. you gotta opt in.

you enable them with SSL_CTX_enable_ct(3) or SSL_enable_ct(3). your call which one, depending on whether you're doing the ctx thing or the single-connection thing 🫶

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🧚 what else can this library do 🧚

not just verification, babe — 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. multitasking icon 💖

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

four whole jobs. she works hard, put some respect on her name 👑

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🌈 SEE ALSO 🌈

go read these next, bestie, they're all connected:

• 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) — yes. it's listed twice. no, we're not fixing it. she said it twice because she meant it 💀
• CT_POLICY_EVAL_CTX_new(3)
• SSL_CTX_set_ct_validation_callback(3)

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⭐ HISTORY ⭐

the ct library was added in OpenSSL 1.1.0. so she's been around a minute, fr fr 🎀

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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>.

like, read the license. it's giving responsible adult energy and we love that for you 🫶

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and that's the page!! this was OpenSSL 3.5.9, dated 2026-09-29 — note it, cite it, screenshot it, whatever, just don't @ me about the duplicate SCT_validate(3). mwah 💋🦋✨