Unicode C++

Verify the RSA Signature of a SHA256 Hash

See more RSA Examples

Demonstrates how to verify an RSA signature of a SHA256 hash. Unicode C++

#include <CkPublicKeyW.h>
#include <CkRsaW.h>
#include <CkBinDataW.h>

void ChilkatSample(void)
    {
    bool success = false;

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

    // Let's say you have a file containing the 32-bytes of a SHA256 hash,
    // and a file that is an RSA signature of those 32 bytes.
    // Here's how you verify using the RSA public key found in a PEM.

    CkPublicKeyW pubKey;
    success = pubKey.LoadFromFile(L"rsaPubKey.pem");
    if (success == false) {
        wprintf(L"%s\n",pubKey.lastErrorText());
        return;
    }

    CkRsaW rsa;

    // Get the public key.
    success = rsa.UsePublicKey(pubKey);
    if (success == false) {
        wprintf(L"%s\n",rsa.lastErrorText());
        return;
    }

    // Get the 32-byte SHA256 hash.
    CkBinDataW bdHash;
    success = bdHash.LoadFile(L"myHash.sha256");
    if (success == false) {
        wprintf(L"Failed to load SHA256 hash.\n");
        return;
    }

    // Get the RSA signature to be validated.
    CkBinDataW bdSig;
    success = bdSig.LoadFile(L"mySig.sig");
    if (success == false) {
        wprintf(L"Failed to load RSA signature.\n");
        return;
    }

    // Verify the signature against the SHA256 hash.
    const wchar_t *enc = L"base64";
    rsa.put_EncodingMode(enc);
    success = rsa.VerifyHashENC(bdHash.getEncoded(enc),L"sha256",bdSig.getEncoded(enc));
    if (success == false) {
        wprintf(L"%s\n",rsa.lastErrorText());
        return;
    }

    wprintf(L"Signature validated.\n");
    }