MYCrypto is a high-level cryptography API for Mac OS X and iPhone. It's an Objective-C wrapper around the system Keychain and CSSM APIs, which are notoriously hard to use, as well as CommonCrypto, which is easier but quite limited.
MYCrypto gives you easy object-oriented interfaces to:
- Symmmetric cryptography (session keys and password-based encryption)
- Asymmetric cryptography (public and private keys; digital signatures)
- Creating and managing identity certificates (for use with SSL and CMS)
- Cryptographic digests/hashes (effectively-unique IDs for data)
- The Keychain (a secure, encrypted storage system for keys and passwords)
- Cryptographic Message Syntax [CMS] for signing/encrypting data
- Parsing and generating ASN.1, BER and DER (the weird binary data formats used by crypto standards)
It's open source, released under a friendly BSD license.