C++

Verfies an RSA Signature

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Verifies an RSA signature against the original data. C++

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

void ChilkatSample(void)
    {
    bool success = false;

    // The following data was signed by the following example:
    // RSA Sign using a Private Key on a USB Token or Smartcard
    CkBinData bd;
    int i;
    for (i = 0; i <= 100; i++) {
        bd.AppendEncoded("000102030405060708090A0B0C0D0E0F","hex");
    }

    // Load the signature
    CkBinData bdSig;
    success = bdSig.LoadFile("rsaSignatures/test1.sig");
    if (success == false) {
        std::cout << "Failed to load the RSA signature" << "\r\n";
        return;
    }

    // Get the public key to be used for signature verification.
    CkPublicKey pubKey;
    success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem");
    if (success == false) {
        std::cout << pubKey.lastErrorText() << "\r\n";
        return;
    }

    CkRsa rsa;
    success = rsa.UsePublicKey(pubKey);
    if (success == false) {
        std::cout << rsa.lastErrorText() << "\r\n";
        return;
    }

    // Verify the hash of the data against the signature.
    // We pass in the original data.  Internally, the hash is generated
    // and used to validate the signature.
    // Validating the RSA signature means two things:  
    // (1) the original data is exactly what was signed, and 
    // (2) it was signed by the owner of the RSA private key.
    success = rsa.VerifyBd(bd,"sha256",bdSig);

    if (success == false) {
        std::cout << rsa.lastErrorText() << "\r\n";
        std::cout << "Signature invalid." << "\r\n";
    }
    else {
        std::cout << "Signature valid." << "\r\n";
    }
    }