(Unicode C++) ECDSA Sign and Verify Data using Different Hash Algorithms

Demonstrates how to create ECDSA signatures on data using different hash algorithms.

Note: This example requires Chilkat v9.5.0.85 or greater because the SignBd and VerifyBd methods were added in v9.5.0.85.

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#include <CkPrivateKeyW.h>
#include <CkBinDataW.h>
#include <CkEccW.h>
#include <CkPrngW.h>
#include <CkPublicKeyW.h>

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

    // First load an ECDSA private key to be used for signing.
    CkPrivateKeyW privKey;
    bool success = privKey.LoadEncryptedPemFile(L"qa_data/ecc/secp256r1-key-pkcs8-secret.pem",L"secret");
    if (success == false) {
        wprintf(L"%s\n",privKey.lastErrorText());
        return;
    }

    // Load some data to be signed.
    CkBinDataW bd;
    success = bd.LoadFile(L"qa_data/hamlet.xml");
    if (success == false) {
        wprintf(L"Failed to load file to be hashed.\n");
        return;
    }

    CkEccW ecdsa;
    CkPrngW prng;

    // Sign the sha256 hash of the data.  Return the ECDSA signature in the base64 encoding.
    wprintf(L"ECDSA signing the sha256 hash of the data...\n");
    const wchar_t *sig = ecdsa.signBd(bd,L"sha256",L"base64",privKey,prng);
    wprintf(L"sig = %s\n",sig);

    // Verify the signature against the original data.
    // (We must use the same hash algorithm that was used when signing.)

    // Load the public key that corresponds to the private key used for signing.
    CkPublicKeyW pubKey;
    success = pubKey.LoadFromFile(L"qa_data/ecc/secp256r1-pub.pem");
    if (success == false) {
        wprintf(L"%s\n",pubKey.lastErrorText());
        return;
    }

    CkEccW ecc2;
    int result = ecc2.VerifyBd(bd,L"sha256",sig,L"base64",pubKey);
    if (result != 1) {
        wprintf(L"%s\n",ecc2.lastErrorText());
        return;
    }

    wprintf(L"Verified!\n");

    // ----------------------------------------------------------------------------------------
    // Let's do the same thing, but with sha384 hashing...

    wprintf(L"--------------------------------------------\n");
    wprintf(L"ECDSA signing the sha384 hash of the data...\n");

    sig = ecdsa.signBd(bd,L"sha384",L"base64",privKey,prng);
    wprintf(L"sig = %s\n",sig);

    result = ecc2.VerifyBd(bd,L"sha384",sig,L"base64",pubKey);
    if (result != 1) {
        wprintf(L"%s\n",ecc2.lastErrorText());
        return;
    }

    wprintf(L"Verified!\n");
    }