Unicode C

ECDSA Sign and Verify Data using Different Hash Algorithms

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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.

Unicode C

#include <C_CkPrivateKeyW.h>
#include <C_CkBinDataW.h>
#include <C_CkEccW.h>
#include <C_CkPrngW.h>
#include <C_CkPublicKeyW.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkPrivateKeyW privKey;
    HCkBinDataW bd;
    HCkEccW ecdsa;
    HCkPrngW prng;
    const wchar_t *sig;
    HCkPublicKeyW pubKey;
    HCkEccW ecc2;
    int result;

    success = FALSE;

    // 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.
    privKey = CkPrivateKeyW_Create();
    success = CkPrivateKeyW_LoadEncryptedPemFile(privKey,L"qa_data/ecc/secp256r1-key-pkcs8-secret.pem",L"secret");
    if (success == FALSE) {
        wprintf(L"%s\n",CkPrivateKeyW_lastErrorText(privKey));
        CkPrivateKeyW_Dispose(privKey);
        return;
    }

    // Load some data to be signed.
    bd = CkBinDataW_Create();
    success = CkBinDataW_LoadFile(bd,L"qa_data/hamlet.xml");
    if (success == FALSE) {
        wprintf(L"Failed to load file to be hashed.\n");
        CkPrivateKeyW_Dispose(privKey);
        CkBinDataW_Dispose(bd);
        return;
    }

    ecdsa = CkEccW_Create();
    prng = CkPrngW_Create();

    // 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");
    sig = CkEccW_signBd(ecdsa,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.
    pubKey = CkPublicKeyW_Create();
    success = CkPublicKeyW_LoadFromFile(pubKey,L"qa_data/ecc/secp256r1-pub.pem");
    if (success == FALSE) {
        wprintf(L"%s\n",CkPublicKeyW_lastErrorText(pubKey));
        CkPrivateKeyW_Dispose(privKey);
        CkBinDataW_Dispose(bd);
        CkEccW_Dispose(ecdsa);
        CkPrngW_Dispose(prng);
        CkPublicKeyW_Dispose(pubKey);
        return;
    }

    ecc2 = CkEccW_Create();
    result = CkEccW_VerifyBd(ecc2,bd,L"sha256",sig,L"base64",pubKey);
    if (result != 1) {
        wprintf(L"%s\n",CkEccW_lastErrorText(ecc2));
        CkPrivateKeyW_Dispose(privKey);
        CkBinDataW_Dispose(bd);
        CkEccW_Dispose(ecdsa);
        CkPrngW_Dispose(prng);
        CkPublicKeyW_Dispose(pubKey);
        CkEccW_Dispose(ecc2);
        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 = CkEccW_signBd(ecdsa,bd,L"sha384",L"base64",privKey,prng);
    wprintf(L"sig = %s\n",sig);

    result = CkEccW_VerifyBd(ecc2,bd,L"sha384",sig,L"base64",pubKey);
    if (result != 1) {
        wprintf(L"%s\n",CkEccW_lastErrorText(ecc2));
        CkPrivateKeyW_Dispose(privKey);
        CkBinDataW_Dispose(bd);
        CkEccW_Dispose(ecdsa);
        CkPrngW_Dispose(prng);
        CkPublicKeyW_Dispose(pubKey);
        CkEccW_Dispose(ecc2);
        return;
    }

    wprintf(L"Verified!\n");


    CkPrivateKeyW_Dispose(privKey);
    CkBinDataW_Dispose(bd);
    CkEccW_Dispose(ecdsa);
    CkPrngW_Dispose(prng);
    CkPublicKeyW_Dispose(pubKey);
    CkEccW_Dispose(ecc2);

    }