C#

RSA Decrypt using Private Key on Smartcard or USB Token via Apple Keychain

See more Apple Keychain Examples

RSA decryption using a certificate's private key located on a hardware token or smartcard via the Apple Keychain.

Note: This example requires Chilkat v10.1.2 or greater.

C#

bool success = false;

//  Beforehand, we generated a 256-bit AES key, RSA encrypted, and saved to a file as in this example:
//  Generate a Random 256-bit AES Key and RSA Encrypt

//  The RSA public key used to encrypt in the above example was obtained from the Apple Keychain
//  like this:
//  Export a Public Key from USB Token or Smartcard using the Apple Keychain

//  This example will load the encrypted data and will RSA decrypt using the 
//  private key of a certificate on a USB token (or smart card) via the Keychain.
//  You can list the Keychain certificates on hardware tokens using the following example:
//  Apple Keychain - List Certs on Smartcards and USB Tokens

//  Get the RSA encrypted data to be decrypted.
Chilkat.BinData bd = new Chilkat.BinData();
//  In all Chilkat methods expecting a path, you can pass either absolute or relative paths.
success = bd.LoadFile("rsaEncrypted/myAes.key");
if (success == false) {
    Debug.WriteLine("Failed to load the encrypted AES key.");
    return;
}

//  Load the certificate having the private key from the Apple Keychain
//  On MacOS and iOS, the LoadByCommonName function will search the Apple Keychain for the matching certificate.
Chilkat.Cert cert = new Chilkat.Cert();

//  To potentially prevent the PIN dialog from being displayed,
//  we'll need to provide the USB token (or smart card) PIN
//  Note: It might not be possible to prevent the PIN dialog from being displayed
//  
cert.SmartCardPin = "123456";

success = cert.LoadByCommonName("Test 2048 bit RSA");
if (success == false) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

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

//  Specify we wish to use the certificate's private key for decryption.
success = rsa.SetX509Cert(cert,true);
if (success == false) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

//  RSA Decrypt
rsa.VerboseLogging = true;
success = rsa.DecryptBd(bd,true);
if (success == false) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

//  The contents of bd are now decrypted.
Debug.WriteLine("Num bytes after decryption: " + Convert.ToString(bd.NumBytes));

//  Some additional notes:
//  
//  If using a Yubikey token, the certificate must be installed in the Key Management slot.
//  The Digital Signature slot is for RSA keys to be used for signing, 
//  and the Key Management slot is for RSA keys to be used for decrypting.
//  

//  If you try to use the RSA key from the Digital Signature slot, you'll get an error such as this:

//  The operation couldn't be completed. 
//  (OSStatus error -50 - algid:encrypt:RSA:PKCS1: algorithm not supported by the key 
//  <SecKeyRef:('com.apple.pivtoken:AF7172EB60DDCBF1D28459AE24398E11') 0x600001ecca90>)