(C# UWP/WinRT) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

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

Chilkat.PrivateKey pkey = new Chilkat.PrivateKey();

// Load the private key from an RSA PEM file:
bool success = pkey.LoadPkcs8EncryptedFile("raul_privateKey.key","a0123456789");

string pkeyXml;
// Get the private key in XML format:
pkeyXml = pkey.GetXml();

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

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

// This example will sign a string, and receive the signature
// in a hex-encoded string.  Therefore, set the encoding mode
// to "hex":
rsa.EncodingMode = "hex";

string strData = "This is the string to be signed.";

// Sign the string using the sha-1 hash algorithm.
// Other valid choices are "md2" and "md5".
string hexSig = rsa.SignStringENC(strData,"sha-1");

Debug.WriteLine(hexSig);

// Now verify with the public key.
// This example shows how to use the public key from 
// a digital certificate (.cer file)
Chilkat.Cert cert = new Chilkat.Cert();
success = cert.LoadFromFile("raul_publicKey.cer");
if (success != true) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

Chilkat.PublicKey pubKey = null;
pubKey = cert.ExportPublicKey();

string pubKeyXml;
// Get the private key in XML format:
pubKeyXml = pubKey.GetXml();

Chilkat.Rsa rsa2 = new Chilkat.Rsa();
success = rsa2.ImportPublicKey(pubKeyXml);
if (success != true) {
    Debug.WriteLine(rsa2.LastErrorText);
    return;
}

// Verify the signature against the original data:
rsa2.EncodingMode = "hex";
success = rsa2.VerifyStringENC(strData,"sha-1",hexSig);
if (success != true) {
    Debug.WriteLine(rsa2.LastErrorText);
    return;
}

Debug.WriteLine("Signature verified!");

// Verify with incorrect data:
success = rsa2.VerifyStringENC("something else","sha-1",hexSig);
if (success != true) {
    Debug.WriteLine("Signature not verified! (which was expected in this case)");
}
else {
    Debug.WriteLine("Hmmm... that's not right...");
}