(Unicode C++) ECDSA Sign Data and Verify Signature

Demonstrates using the Elliptic Curve Digital Signature Algorithm to hash data and sign it. Also demonstrates how to verify the ECDSA signature.

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#include <CkCrypt2W.h>
#include <CkPrivateKeyW.h>
#include <CkPrngW.h>
#include <CkEccW.h>
#include <CkPublicKeyW.h>

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

    // To create an ECDSA signature, the data first needs to be hashed.  Then the hash
    // is signed.

    // Use Chilkat Crypt2 to generate a hash for any of the following
    // hash algorithms: SHA256, SHA384, SHA512, SHA1, MD5, MD2, HAVAL, RIPEMD128/160/256/320

    CkCrypt2W crypt;
    crypt.put_HashAlgorithm(L"SHA256");
    crypt.put_Charset(L"utf-8");
    crypt.put_EncodingMode(L"base64");

    // Hash a string.
    const wchar_t *hash1 = crypt.hashStringENC(L"The quick brown fox jumps over the lazy dog");
    wprintf(L"hash1 = %s\n",hash1);

    // Or hash a file..
    const wchar_t *hash2 = crypt.hashFileENC(L"qa_data/hamlet.xml");
    wprintf(L"hash2 = %s\n",hash2);

    // (The Crypt2 API provides many other ways to hash data..)

    // -----------------------------------------------------------
    // An ECDSA private key is used for signing.  The public key is for signature verification.
    // Load our ECC private key.
    // Our private key file contains this:

    // 	// -----BEGIN PRIVATE KEY-----
    // 	MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
    // 	72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
    // 	a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
    // 	-----END PRIVATE KEY-----

    CkPrivateKeyW privKey;
    bool success = privKey.LoadPemFile(L"qa_data/ecc/secp256r1-key-pkcs8.pem");
    if (success != true) {
        wprintf(L"%s\n",privKey.lastErrorText());
        return;
    }

    // We'll need a PRNG source for random number generation.
    // Use Chilkat's PRNG (for the Fortuna PRNG algorithm).
    CkPrngW prng;

    // Sign the hash..
    CkEccW ecdsa;
    const wchar_t *ecdsaSigBase64 = ecdsa.signHashENC(hash1,L"base64",privKey,prng);
    if (ecdsa.get_LastMethodSuccess() != true) {
        wprintf(L"%s\n",ecdsa.lastErrorText());
        return;
    }

    wprintf(L"ECDSA signature = %s\n",ecdsaSigBase64);

    // -----------------------------------------------------------
    // Now let's verify the signature using the public key.

    CkPublicKeyW pubKey;
    success = pubKey.LoadFromFile(L"qa_data/ecc/secp256r1-pubkey.pem");
    if (success != true) {
        wprintf(L"%s\n",pubKey.lastErrorText());
        return;
    }

    int result = ecdsa.VerifyHashENC(hash1,ecdsaSigBase64,L"base64",pubKey);
    if (result == 1) {
        wprintf(L"Signature is valid.\n");
        return;
    }

    if (result == 0) {
        wprintf(L"Signature is invalid.\n");
        return;
    }

    if (result < 0) {
        wprintf(L"%s\n",ecdsa.lastErrorText());
        wprintf(L"The VerifyHashENC method call failed.\n");
        return;
    }
    }