Keychain Services

Secure credential storage, SecItem API mental model, uniqueness constraints, data protection classes, biometric access control, keychain sharing, and Mac keychain differences for iOS/macOS apps.

When to Use This Skill

Use when you need to:

• ☑ Store tokens, passwords, API keys, or cryptographic keys securely
• ☑ Debug errSecDuplicateItem, errSecItemNotFound, or errSecInteractionNotAllowed
• ☑ Choose the right kSecAttrAccessible level for your use case
• ☑ Add biometric or passcode protection to a keychain item
• ☑ Share credentials between apps or app extensions via access groups
• ☑ Migrate from UserDefaults/@AppStorage to keychain for sensitive data
• ☑ Understand why SecItemCopyMatching returns something different than expected
• ☑ Store or retrieve keychain items from a background context

Example Prompts