# Certificate, Key, and Trust Services Establish trust using certificates and cryptographic keys. ## Overview The certificate, key, and trust services API is a collection of functions and data structures that you use to conduct secure and authenticated data transactions. Specifically, you use this API to manage and use: - **Certificates and identities.** A certificate is a collection of data that identifies its owner in a tamper-evident way. When you use a certificate to distribute a public key, a receiver can be confident of its origin. You can also package a certificate together with its corresponding private key in an identity object that you keep secret. - **Policies and trust services.** When you receive a certificate, before you can use the embedded public key, you have to answer the question, “Can I trust this certificate?” You conduct an evaluation of trust according to a set of criteria, or a trust policy. - **Cryptographic keys.** After you have a key whose origin you trust, you can begin to conduct cryptographic operations, such as encryption or data signing and verification. These operations in turn typically serve a larger purpose, such as authenticating a user, transmitting data securely, or verifying that a block of data is unaltered since being sealed with a signature. > Note: > Rely on the classes of the framework to ensure a consistent experience when displaying certificates and trust settings to the user and when the user chooses among identities or modifies keychain settings. ## Topics ### API Components [Certificates](/documentation/Security/certificates) Manage digital certificates. [Keys](/documentation/Security/keys) Generate, store, and use cryptographic keys. [Identities](/documentation/Security/identities) Combine certificates and cryptographic keys into identities. [Policies](/documentation/Security/policies) Obtain policies for establishing trust. [Trust](/documentation/Security/trust) Evaluate trust based on a given policy. ### Thread Safety [Working with Concurrency](/documentation/Security/working-with-concurrency) Learn about thread safety issues related to the certificate, key, and trust services API. ## See Also [Cryptographic Services Guide](https://developer.apple.com/library/archive/documentation/Security/Conceptual/cryptoservices/Introduction/Introduction.html#//apple_ref/doc/uid/TP40011172) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)