(Mono C#) 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.

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

Chilkat.PublicKey pubKey = new Chilkat.PublicKey();

// Load the public key from an PEM file:
bool success = pubKey.LoadFromFile("pubKey.pem");
if (success != true) {
    Debug.WriteLine(pubKey.LastErrorText);
    return;
}

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

// Load the signature.
Chilkat.BinData bdSig = new Chilkat.BinData();
success = bdSig.LoadFile("signature.sig");

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

// Import the public key into the RSA component:
success = rsa.ImportPublicKeyObj(pubKey);
if (success != true) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

// OpenSSL uses big-endian.
rsa.LittleEndian = false;

success = rsa.VerifyBd(bdFileData,"sha256",bdSig);
if (success != true) {
    Debug.WriteLine(rsa.LastErrorText);
    Debug.WriteLine("The signature was invalid.");
    return;
}

Debug.WriteLine("The signature was verified.");