(C++) 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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#include <CkPrivateKey.h>
#include <CkPublicKey.h>
#include <CkEdDSA.h>

void ChilkatSample(void)
    {
    // 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

    const char *alicePrivKey = "77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a";
    const char *bobPubKey = "de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f";

    CkPrivateKey privKey;
    // 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.
    bool success = privKey.LoadEd25519(alicePrivKey,"");
    if (success == false) {
        std::cout << privKey.lastErrorText() << "\r\n";
        return;
    }

    CkPublicKey pubKey;
    success = pubKey.LoadEd25519(bobPubKey);
    if (success == false) {
        std::cout << pubKey.lastErrorText() << "\r\n";
        return;
    }

    // Create the shared secret:
    CkEdDSA eddsa;
    const char *sharedSecret = eddsa.sharedSecretENC(privKey,pubKey,"hexlower");
    if (eddsa.get_LastMethodSuccess() == false) {
        std::cout << eddsa.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Computed: " << sharedSecret << "\r\n";
    std::cout << "Expected: 4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742" << "\r\n";
    }