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# NSRequiresCertificateTransparency

An obsolete Boolean value indicating whether to require Certificate Transparency.

## Discussion

Certificate Transparency (CT) is a protocol that ATS can use to identify mistakenly or maliciously issued X.509 certificates. Earlier versions of the system used this key to enable or disable CT for a given domain. Specifically, CT requires a domain’s server certificates to have support from signed CT timestamps from at least two CT logs trusted by Apple. For more information about Certificate Transparency, see [RFC 6962](https://tools.ietf.org/html/rfc6962).

The system now requires this behavior in all cases, making the key irrelevant.

> Warning:
> Don’t use this key. The current system enforces this behavior, and new certificates can’t meet the requirement on older systems.

---

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