C#

Verfies an RSA Signature

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Verifies an RSA signature against the original data. C#

bool success = false;

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

//  Load the signature
Chilkat.BinData bdSig = new Chilkat.BinData();
success = bdSig.LoadFile("rsaSignatures/test1.sig");
if (success == false) {
    Debug.WriteLine("Failed to load the RSA signature");
    return;
}

//  Get the public key to be used for signature verification.
Chilkat.PublicKey pubKey = new Chilkat.PublicKey();
success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem");
if (success == false) {
    Debug.WriteLine(pubKey.LastErrorText);
    return;
}

Chilkat.Rsa rsa = new Chilkat.Rsa();
success = rsa.UsePublicKey(pubKey);
if (success == false) {
    Debug.WriteLine(rsa.LastErrorText);
    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) {
    Debug.WriteLine(rsa.LastErrorText);
    Debug.WriteLine("Signature invalid.");
}
else {
    Debug.WriteLine("Signature valid.");
}