C#

RSA Sign an Encoded Hash

See more RSA Examples

Demonstrates signing a hash (e.g., SHA256) provided as an encoded string (e.g., base64 or hex). C#

bool success = false;

//  Assuming the smartcard/USB token is installed with the correct drivers from the manufacturer,
//  this code can work on multiple platforms including Windows, MacOS, Linux, and iOS.

//  Chilkat automatically detects and determines the way in which the HSM is used,
//  which can be by PKCS11, Apple Keychain, Microsoft CNG / Crypto API, or ScMinidriver.

Chilkat.Cert cert = new Chilkat.Cert();

//  Set the token/smartcard PIN prior to loading.
cert.SmartCardPin = "123456";

//  Specify the certificate by its common name.
success = cert.LoadFromSmartcard("cn=chilkat-rsa-2048");
if (success == false) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

Debug.WriteLine("Signing with the private key for this cert: " + cert.SubjectCN);

//  Create data to be hashed and signed.
Chilkat.BinData bd = new Chilkat.BinData();
int i;
for (i = 0; i <= 100; i++) {
    bd.AppendEncoded("000102030405060708090A0B0C0D0E0F","hex");
}

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

//  Use the certificate's private key for signing.
success = rsa.SetX509Cert(cert,true);
if (success == false) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

//  We'll first compute the hash and then pass the encoded hash to be signed.
string sha256_base64 = bd.GetHash("sha256","base64");
Debug.WriteLine("sha256 hash in base64 format: " + sha256_base64);

//  Pass in the base64 hash and return a base64 signature.
rsa.EncodingMode = "base64";
string rsaSig_base64 = rsa.SignHashENC(sha256_base64,"sha256");
if (success == false) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

Debug.WriteLine("RSA signature as base64: " + rsaSig_base64);