(Swift 2) Duplicate .NET's Rfc2898DeriveBytes Functionality

Demonstrates how to duplicate the results produced by .NET's System.Security.Cryptography.Rfc2898DeriveBytes class.

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func chilkatTest() {
    // This example assumes Chilkat Crypt2 to have been previously unlocked.
    // See Unlock Crypt2 for sample code.

    // This example demonstrates how to duplicate the results produced
    // by .NET's System.Security.Cryptography.Rfc2898DeriveBytes class.

    // For example, here is C# code that transforms a password string into
    // bytes that can be used as a secret key for symmetric encryption (such as AES, blowfish, 3DES, etc.)
    // 
    //     Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes("secret", System.Text.Encoding.UTF8.GetBytes("saltsalt123"), numIterations);
    //     byte[] secretKeyBytes = deriveBytes.GetBytes(numBytes);

    // (The Rfc2898DeriveBytes computation is really just the PBKDF2 algorithm with SHA-1 hashing.)
    // In Chilkat, this is what we do to match...

    // First, let's get a test vector with known results.  Both Chilkat AND Microsoft should produce
    // the same results.  RFC 6070 has some PBKDF2 HMAC-SHA1 Test Vectors.  Here is one of them:

    //      Input:
    //        P = "passwordPASSWORDpassword" (24 octets)
    //        S = "saltSALTsaltSALTsaltSALTsaltSALTsalt" (36 octets)
    //        c = 4096
    //        dkLen = 25
    // 
    //      Output:
    //        DK = 3d 2e ec 4f e4 1c 84 9b
    //             80 c8 d8 36 62 c0 e4 4a
    //             8b 29 1a 96 4c f2 f0 70
    //             38                      (25 octets)
    // 
    // 

    let crypt = CkoCrypt2()

    var salt: String? = "saltSALTsaltSALTsaltSALTsaltSALTsalt"
    // Given that the salt is really binary data (can be any random bunch of bytes),
    // we must pass the exact hex string representation of the salt bytes.
    // In this case, we're getting the utf-8 byte representation of our salt string,
    // which is identical to the us-ascii byte representation because there are no 8bit chars..
    var saltHex: String? = crypt.EncodeString(salt, charset: "utf-8", encoding: "hex")

    // Duplicate the test vector as shown above.
    var dkHex: String? = crypt.Pbkdf2("passwordPASSWORDpassword", charset: "utf-8", hashAlg: "sha1", salt: saltHex, iterationCount: 4096, outputKeyBitLen: 25 * 8, encoding: "hex")
    print("\(dkHex!)")

}