How to use Keychain access to store passwords in iPhone App?

Can s开发者_JAVA百科omeone tell me how we can store information in Keychain? How secure it would be?

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"What you’re left with is an encrypted flat-file database, specialized for just a few data types, with a really clunky and badly documented API. As I wrote above, its functionality could be duplicated, with a better API, without much effort. The encryption part is significant, though, since its primary purpose is to keep keys and passwords safe. A DIY key database could be protected by encrypting it with a symmetric key, and then putting that key in the Keychain."