(MFC) Duplicate openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

Demonstrates how to duplicate this OpenSSL command:

openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

1. Creates a SHA256 digest of the contents of the input file.
2. Verifies the SHA256 digest using the public key.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkPublicKey.h>
#include <CkBinData.h>
#include <CkRsa.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkPublicKey pubKey;

    // Load the public key from an PEM file:
    bool success = pubKey.LoadOpenSslPemFile("pubKey.pem");
    if (success != true) {
        strOut.append(pubKey.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Load the data of the original file that was signed.
    CkBinData bdFileData;
    success = bdFileData.LoadFile("in.dat");

    // Load the signature.
    CkBinData bdSig;
    success = bdSig.LoadFile("signature.sig");

    CkRsa rsa;

    // Import the public key into the RSA component:
    success = rsa.ImportPublicKeyObj(pubKey);
    if (success != true) {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // OpenSSL uses big-endian.
    rsa.put_LittleEndian(false);

    success = rsa.VerifyBd(bdFileData,"sha256",bdSig);
    if (success != true) {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
        strOut.append("The signature was invalid.");
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("The signature was verified.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }