(Mono C#) RSA Sign String using Private Key of Certificate Type A3 (smart card / token)

Demonstrates RSA signing a string using the private key of a certificate type A3 (smart card, token).

Note: This is a Windows-only example.

Chilkat .NET Downloads Chilkat .NET Assemblies Chilkat for .NET Core Chilkat for Mono

// First get the A3 certificate that was installed on the Windows system.
Chilkat.CertStore certStore = new Chilkat.CertStore();

string thumbprint = "12c1dd8015f3f03f7b1fa619dc24e2493ca8b4b2";

// This is specific to Windows because it is opening the Windows Current-User certificate store.
bool bReadOnly = true;
bool success = certStore.OpenCurrentUserStore(bReadOnly);
if (success != true) {
    Debug.WriteLine(certStore.LastErrorText);
    return;
}

// Find the certificate with the desired thumbprint
// (There are many ways to locate a certificate.  This example chooses to find by thumbprint.)
Chilkat.Cert cert = certStore.FindCertBySha1Thumbprint(thumbprint);
if (certStore.LastMethodSuccess != true) {
    Debug.WriteLine("Failed to find the certificate.");
    return;
}

Debug.WriteLine("Found: " + cert.SubjectCN);

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

// Provide the cert's private key
bool bUsePrivateKey = true;
success = rsa.SetX509Cert(cert,bUsePrivateKey);

if (success != true) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

// Return the RSA signature in base64 encoded form.
rsa.EncodingMode = "base64";

// Sign the utf-8 byte representation of the string.
rsa.Charset = "utf-8";

// You can also choose other hash algorithms, such as SHA-1.
string sigBase64 = rsa.SignStringENC("text to sign","SHA-256");
if (rsa.LastMethodSuccess != true) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

Debug.WriteLine("Base64 signature: " + sigBase64);