(Objective-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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#import <NSString.h>
#import <CkoPrivateKey.h>
#import <CkoPublicKey.h>
#import <CkoEdDSA.h>

// 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

NSString *alicePrivKey = @"77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a";
NSString *bobPubKey = @"de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f";

CkoPrivateKey *privKey = [[CkoPrivateKey alloc] init];
// 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 pubKey: @""];
if (success == NO) {
    NSLog(@"%@",privKey.LastErrorText);
    return;
}

CkoPublicKey *pubKey = [[CkoPublicKey alloc] init];
success = [pubKey LoadEd25519: bobPubKey];
if (success == NO) {
    NSLog(@"%@",pubKey.LastErrorText);
    return;
}

// Create the shared secret:
CkoEdDSA *eddsa = [[CkoEdDSA alloc] init];
NSString *sharedSecret = [eddsa SharedSecretENC: privKey pubkey: pubKey encoding: @"hexlower"];
if (eddsa.LastMethodSuccess == NO) {
    NSLog(@"%@",eddsa.LastErrorText);
    return;
}

NSLog(@"%@%@",@"Computed: ",sharedSecret);
NSLog(@"%@",@"Expected: 4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742");