C#

Verify the RSA Signature of a SHA256 Hash

See more RSA Examples

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

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.

Chilkat.PublicKey pubKey = new Chilkat.PublicKey();
success = pubKey.LoadFromFile("rsaPubKey.pem");
if (success == false) {
    Debug.WriteLine(pubKey.LastErrorText);
    return;
}

Chilkat.Rsa rsa = new Chilkat.Rsa();

// Get the public key.
success = rsa.UsePublicKey(pubKey);
if (success == false) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

// Get the 32-byte SHA256 hash.
Chilkat.BinData bdHash = new Chilkat.BinData();
success = bdHash.LoadFile("myHash.sha256");
if (success == false) {
    Debug.WriteLine("Failed to load SHA256 hash.");
    return;
}

// Get the RSA signature to be validated.
Chilkat.BinData bdSig = new Chilkat.BinData();
success = bdSig.LoadFile("mySig.sig");
if (success == false) {
    Debug.WriteLine("Failed to load RSA signature.");
    return;
}

// Verify the signature against the SHA256 hash.
string enc = "base64";
rsa.EncodingMode = enc;
success = rsa.VerifyHashENC(bdHash.GetEncoded(enc),"sha256",bdSig.GetEncoded(enc));
if (success == false) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

Debug.WriteLine("Signature validated.");