(Swift 3,4,5...) RSA Encrypt and Decrypt Credit Card Numbers

Swift 3,4,5... sample code to RSA public-key encrypt and decrypt credit card numbers. The RSA key is loaded from an unencrypted PKCS8 file. Chilkat provides many ways of setting the key -- loading from both encrypted and unencrypted PEM, PKCS8, DER, PVK, etc. Keys may be loaded from files or in-memory representations. (The RSA component also provides the ability to generate RSA keys.)

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

    let rsa = CkoRsa()!

    let key = CkoPrivateKey()!

    // Load an RSA private key from a file:
    var success: Bool = key.loadAnyFormatFile("rsaPrivateKey.key", password: "")
    if success != true {
        print("\(key.lastErrorText!)")
        return
    }

    // Get the key as XML:
    var keyXml: String?
    keyXml = key.getXml()

    // We'll encrypt with the public key and decrypt with the private
    // key.  (It's also possible to do the reverse.)
    // Note: An RSA private key is composed of different parts internally: modulus, exponent, P, Q, etc.
    // An RSA public-key is a sub-set of the private key.
    // Therefore, when you have a private key, you really have
    // both public and private keys.
    success = rsa.importPublicKey(keyXml)
    if success != true {
        print("\(rsa.lastErrorText!)")
        return
    }

    // Encrypt a VISA credit card number:
    // 1234-5678-0000-9999
    var ccNumber: String? = "1234567800009999"

    var usePrivateKey: Bool = false
    rsa.encodingMode = "base64"
    var encryptedStr: String? = rsa.encryptStringENC(ccNumber, bUsePrivateKey: usePrivateKey)
    print("Encrypted:")
    print("\(encryptedStr!)")

    // Now decrypt:
    let rsaDecryptor = CkoRsa()!

    rsaDecryptor.encodingMode = "base64"
    success = rsaDecryptor.importPrivateKey(keyXml)

    usePrivateKey = true
    var decryptedStr: String? = rsaDecryptor.decryptStringENC(encryptedStr, bUsePrivateKey: usePrivateKey)

    print("Decrypted:")
    print("\(decryptedStr!)")

    // Important: RSA encryption should only be used to encrypt small amounts of data.
    // It is typically used for encrypting symmetric encryption
    // keys such that a symmetric encryption algorithm, such as 
    // AES is then used to encrypt/decrypt bulk data

}