Unicode C

Create ECSDA Signature using Raw r and s Format (not ASN.1)

See more ECC Examples

Demonstrates how to create an ECDSA signature using the raw r/s format.

ECDSA signatures have two equal sized parts, r and s. There are two common formats for encoding the signature:

(a) Concatenating the raw byte array of r and s
(b) Encoding both into a structured ASN.1 / DER sequence.

This example demonstrates how to create a signature that is a byte array of r and s concatenated.

Note: This example requires Chilkat v9.5.0.97 or greater.

Unicode C

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

void ChilkatSample(void)
    {
    BOOL success;
    HCkStringBuilderW sb;
    const wchar_t *hash;
    HCkPrivateKeyW privKey;
    HCkPrngW prng;
    HCkEccW ecdsa;
    const wchar_t *ecdsaSigBase64;
    HCkPublicKeyW pubKey;
    int result;

    success = FALSE;

    // 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.

    sb = CkStringBuilderW_Create();
    CkStringBuilderW_Append(sb,L"The quick brown fox jumps over the lazy dog");
    hash = CkStringBuilderW_getHash(sb,L"sha256",L"base64",L"utf-8");

    // Load the ECDSA key to be used for signing.
    privKey = CkPrivateKeyW_Create();
    success = CkPrivateKeyW_LoadPemFile(privKey,L"qa_data/ecc/secp256r1-key-pkcs8.pem");
    if (success != TRUE) {
        wprintf(L"%s\n",CkPrivateKeyW_lastErrorText(privKey));
        CkStringBuilderW_Dispose(sb);
        CkPrivateKeyW_Dispose(privKey);
        return;
    }

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

    // Produce a signature that is not ASN.1, but is instead the concatenation
    // of the raw r and s signature parts.
    // This feature was added in Chilkat v9.5.0.97
    CkEccW_putAsnFormat(ecdsa,FALSE);

    ecdsaSigBase64 = CkEccW_signHashENC(ecdsa,hash,L"base64",privKey,prng);
    if (CkEccW_getLastMethodSuccess(ecdsa) != TRUE) {
        wprintf(L"%s\n",CkEccW_lastErrorText(ecdsa));
        CkStringBuilderW_Dispose(sb);
        CkPrivateKeyW_Dispose(privKey);
        CkPrngW_Dispose(prng);
        CkEccW_Dispose(ecdsa);
        return;
    }

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

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

    pubKey = CkPublicKeyW_Create();
    success = CkPublicKeyW_LoadFromFile(pubKey,L"qa_data/ecc/secp256r1-pubkey.pem");
    if (success != TRUE) {
        wprintf(L"%s\n",CkPublicKeyW_lastErrorText(pubKey));
        CkStringBuilderW_Dispose(sb);
        CkPrivateKeyW_Dispose(privKey);
        CkPrngW_Dispose(prng);
        CkEccW_Dispose(ecdsa);
        CkPublicKeyW_Dispose(pubKey);
        return;
    }

    // Note: When verifying, Chilkat will auto-detect the format for both kinds of ECDSA signatures (ASN.1 or binary r+s)
    result = CkEccW_VerifyHashENC(ecdsa,hash,ecdsaSigBase64,L"base64",pubKey);
    if (result == 1) {
        wprintf(L"Signature is valid.\n");
        CkStringBuilderW_Dispose(sb);
        CkPrivateKeyW_Dispose(privKey);
        CkPrngW_Dispose(prng);
        CkEccW_Dispose(ecdsa);
        CkPublicKeyW_Dispose(pubKey);
        return;
    }

    if (result == 0) {
        wprintf(L"Signature is invalid.\n");
        CkStringBuilderW_Dispose(sb);
        CkPrivateKeyW_Dispose(privKey);
        CkPrngW_Dispose(prng);
        CkEccW_Dispose(ecdsa);
        CkPublicKeyW_Dispose(pubKey);
        return;
    }

    if (result < 0) {
        wprintf(L"%s\n",CkEccW_lastErrorText(ecdsa));
        wprintf(L"The VerifyHashENC method call failed.\n");
        CkStringBuilderW_Dispose(sb);
        CkPrivateKeyW_Dispose(privKey);
        CkPrngW_Dispose(prng);
        CkEccW_Dispose(ecdsa);
        CkPublicKeyW_Dispose(pubKey);
        return;
    }



    CkStringBuilderW_Dispose(sb);
    CkPrivateKeyW_Dispose(privKey);
    CkPrngW_Dispose(prng);
    CkEccW_Dispose(ecdsa);
    CkPublicKeyW_Dispose(pubKey);

    }