(Swift 2) AES and CHACHA20 Encrypt/Decrypt Text

Demonstrates the use of the new EncryptSb and DecryptSb methods introduced in Chilkat v9.5.0.67 to encrypt/decrypt the contents of StringBuilder objects.

Note: This example requires Chilkat v9.5.0.67 or greater.

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

    var success: Bool

    // First build a string to be encrypted
    let sb = CkoStringBuilder()
    var i: Int = 1
    while i < 10 {
        sb.AppendInt(i)
        sb.Append(" the quick brown fox jumped over the lazy dog.\r\n")
        i = i + 1
    }

    print("\(sb.GetAsString())")

    // The string to be encrypted looks like this:

    // 1 the quick brown fox jumped over the lazy dog.
    // 2 the quick brown fox jumped over the lazy dog.
    // 3 the quick brown fox jumped over the lazy dog.
    // 4 the quick brown fox jumped over the lazy dog.
    // 5 the quick brown fox jumped over the lazy dog.
    // 6 the quick brown fox jumped over the lazy dog.
    // ...

    let crypt = CkoCrypt2()

    // Specify the encryption to be used.
    // First we'll do AES-128 CBC
    crypt.CryptAlgorithm = "aes"
    crypt.CipherMode = "cbc"
    crypt.KeyLength = 128

    var ivHex: String? = "000102030405060708090A0B0C0D0E0F"
    crypt.SetEncodedIV(ivHex, encoding: "hex")

    var keyHex: String? = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F"
    crypt.SetEncodedKey(keyHex, encoding: "hex")

    // When EncryptSb is called, the contents of the source (sb)
    // remains unmodified.  The encrypted bytes are written into bdEncrypted.
    // If bdEncrypted already contained data, it is replaced with the encrypted bytes.
    let bdEncrypted = CkoBinData()
    success = crypt.EncryptSb(sb, bdOut: bdEncrypted)
    if success != true {
        print("\(crypt.LastErrorText)")
        return
    }

    // Examine the encrypted bytes:
    print("\(bdEncrypted.GetEncoded("base64_mime"))")

    // Sample encrypted data:

    // 0DdNZ22ckMMJBiaKhAu3wUEfh16XW356NIUsDmNs/xwbHe/p1201OmpfzwXwKktkAefu2pckrBgC
    // df+1w8lRo+KAy5n5wlAgMGM/UrsVJsp0BmDPk1vaxKrmrGpSXOVCQs1n2+0atIs5YLiOG+Va3+Mi
    // EQNb4YK7bNMmvt0++irBxTiGnkx/RncfKwgkbBUpl2x7yV13MW6lapDT6Md0DKAMsTXFJYGeIdEf
    // g2uxDDQzI5gUOUHTMrXQ8paD/K76KKB9Jpp/kAM9z8g/d8KUmuphA7KI64d38xsgOmcITlbhlCQ2
    // PDkcU6RRzX0FUTUSMgQukhy0jkLZEjHX9poKJD+iJTOkcQUC3OqR9hKhSrvIgJN4lxdR71MheOoQ
    // 2wmvRdq+agTWWh333Vmb6J6yDV79aSpnqEDrA8Ks7Xzciol0gve91+JtVJlJKjWwEzWEU8GxF7Q8
    // eaWI70lsC5nTLGcbqgKu6gzkzHlHyHaE2FAQA/d5I2dvfsAYUQCza0Zdyw8mmTtHhlP2Tfxj1uPv
    // H4Q7BGuKnx3SWT2CnpbX4091w7KzLAztrbFBo/Tf9w8ZpgTK9k1ryfW9/xnk6rW6iQ==

    // Decrypt to restore back to the original:
    let sbOriginal = CkoStringBuilder()
    success = crypt.DecryptSb(bdEncrypted, sbOut: sbOriginal)
    if success != true {
        print("\(crypt.LastErrorText)")
        return
    }

    // Examine the original data:
    print("\(sbOriginal.GetAsString())")

    // ----------------------------------------------------------------------------------
    // To do chacha20 encryption, just change the settings:

    crypt.CryptAlgorithm = "chacha20"
    crypt.KeyLength = 256
    // The initial count is the initial block counter for the chacha20 algorithm.
    // It can be any integer, but must be set to the same when decrypting.
    crypt.InitialCount = 22

    // EncryptSb completely replaces the contents of bdEncrypted.
    success = crypt.EncryptSb(sb, bdOut: bdEncrypted)

    // However.. DecryptSb appends the decrypted text to whatever may
    // have already existed within sbOriginal.
    success = crypt.DecryptSb(bdEncrypted, sbOut: sbOriginal)

    print("----")
    print("The original data should be here twice.  Once from the AES decrypt, and again from the chacha20 decrypt.")
    print("\(sbOriginal.GetAsString())")
    print("Success.")

}