(Delphi DLL) RSA Encrypt and Decrypt Credit Card Numbers

Delphi DLL sample code to RSA public-key encrypt and decrypt credit card numbers. The RSA key is loaded from an unencrypted PKCS8 file. Chilkat provides many ways of setting the key -- loading from both encrypted and unencrypted PEM, PKCS8, DER, PVK, etc. Keys may be loaded from files or in-memory representations. (The RSA component also provides the ability to generate RSA keys.)

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, PrivateKey, Rsa;

...

procedure TForm1.Button1Click(Sender: TObject);
var
rsa: HCkRsa;
key: HCkPrivateKey;
success: Boolean;
keyXml: PWideChar;
ccNumber: PWideChar;
usePrivateKey: Boolean;
encryptedStr: PWideChar;
rsaDecryptor: HCkRsa;
decryptedStr: PWideChar;

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

rsa := CkRsa_Create();

key := CkPrivateKey_Create();

// Load an RSA private key from a file:
success := CkPrivateKey_LoadAnyFormatFile(key,'rsaPrivateKey.key','');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkPrivateKey__lastErrorText(key));
    Exit;
  end;

// Get the key as XML:

keyXml := CkPrivateKey__getXml(key);

// We'll encrypt with the public key and decrypt with the private
// key.  (It's also possible to do the reverse.)
// Note: An RSA private key is composed of different parts internally: modulus, exponent, P, Q, etc.
// An RSA public-key is a sub-set of the private key.
// Therefore, when you have a private key, you really have
// both public and private keys.
success := CkRsa_ImportPublicKey(rsa,keyXml);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

// Encrypt a VISA credit card number:
// 1234-5678-0000-9999
ccNumber := '1234567800009999';

usePrivateKey := False;
CkRsa_putEncodingMode(rsa,'base64');
encryptedStr := CkRsa__encryptStringENC(rsa,ccNumber,usePrivateKey);
Memo1.Lines.Add('Encrypted:');
Memo1.Lines.Add(encryptedStr);

// Now decrypt:
rsaDecryptor := CkRsa_Create();

CkRsa_putEncodingMode(rsaDecryptor,'base64');
success := CkRsa_ImportPrivateKey(rsaDecryptor,keyXml);

usePrivateKey := True;
decryptedStr := CkRsa__decryptStringENC(rsaDecryptor,encryptedStr,usePrivateKey);

Memo1.Lines.Add('Decrypted:');
Memo1.Lines.Add(decryptedStr);

// Important: RSA encryption should only be used to encrypt small amounts of data.
// It is typically used for encrypting symmetric encryption
// keys such that a symmetric encryption algorithm, such as 
// AES is then used to encrypt/decrypt bulk data

CkRsa_Dispose(rsa);
CkPrivateKey_Dispose(key);
CkRsa_Dispose(rsaDecryptor);

end;