SQLCipher provides fully transparent encryption of SQLite databases. SQLCipher is a specialized build of the SQLite database that performs transparent and on-the-fly encryption. Using SQLCipher, an application uses the standard SQLite API to manipulate tables using SQL. Behind the scenes, the library silently manages security, making sure that data pages are encrypted and decrypted as they are written to and read from storage. SQLCipher relies on the peer-reviewed OpenSSL library for several encryption requirements, including the AES-256 algorithm, pseudo random number generation, and PBKDF2 key derivation.
LibRCrypt is an Objective C library for complex data encryption based on Rubik's Cubes. The idea's pretty simple: If you represent data as the squares on a Rubik's Cube, you can apply transformations to the data and get back encrypted data, all of which is commutatitive. Just as a Rubik's Cube can be solved if you know all of the moves, this data can be "unwound", so to speak, if you know all of the transforms applied, but the encryption is even deeper than that. A cube can only cover (9 squares per face x 6 faces) 54 significant bits of data. Therefore, compressed data must be composed of multiple (even thousands) of Rubik's Cubes.