(Swift 3,4,5...) Ed25519 Key Exchange (Shared Secret)

Demonstrates how to create an Ed25519 shared secret for use in key exchange.

Note: This example requires Chilkat v9.5.0.83 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.

    // Alice's private key, a:
    //     77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a
    // Alice's public key, X25519(a, 9):
    //     8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a
    // Bob's private key, b:
    //     5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb
    // Bob's public key, X25519(b, 9):
    //     de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f
    // Their shared secret, K:
    //     4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742

    var alicePrivKey: String? = "77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a"
    var bobPubKey: String? = "de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f"

    let privKey = CkoPrivateKey()!
    // This example shows only one way of loading an Ed25519 private key.
    // Chilkat can load other formats (JWK, PEM, ASN.1 DER, etc.)  
    // You may do so by calling LoadAnyFormat or LoadAnyFormatFile.
    var success: Bool = privKey.loadEd25519(alicePrivKey, pubKey: "")
    if success == false {
        print("\(privKey.lastErrorText!)")
        return
    }

    let pubKey = CkoPublicKey()!
    success = pubKey.loadEd25519(bobPubKey)
    if success == false {
        print("\(pubKey.lastErrorText!)")
        return
    }

    // Create the shared secret:
    let eddsa = CkoEdDSA()!
    var sharedSecret: String? = eddsa.sharedSecretENC(privKey, pubkey: pubKey, encoding: "hexlower")
    if eddsa.lastMethodSuccess == false {
        print("\(eddsa.lastErrorText!)")
        return
    }

    print("Computed: \(sharedSecret!)")
    print("Expected: 4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742")

}