(Delphi ActiveX) RSA Encrypt and Decrypt Strings

Delphi ActiveX sample code to RSA public-key encrypt and decrypt strings using public and private keys.

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

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
rsa: TChilkatRsa;
success: Integer;
publicKey: WideString;
privateKey: WideString;
plainText: WideString;
rsaEncryptor: TChilkatRsa;
usePrivateKey: Integer;
encryptedStr: WideString;
rsaDecryptor: TChilkatRsa;
decryptedStr: WideString;

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

rsa := TChilkatRsa.Create(Self);

// This example also generates the public and private
// keys to be used in the RSA encryption.
// Normally, you would generate a key pair once,
// and distribute the public key to your partner.
// Anything encrypted with the public key can be
// decrypted with the private key.  The reverse is 
// also true: anything encrypted using the private
// key can be decrypted using the public key.

// Generate a 1024-bit key.  Chilkat RSA supports
// key sizes ranging from 512 bits to 4096 bits.
success := rsa.GenerateKey(1024);
if (success <> 1) then
  begin
    Memo1.Lines.Add(rsa.LastErrorText);
    Exit;
  end;

// Keys are exported in XML format:
publicKey := rsa.ExportPublicKey();
privateKey := rsa.ExportPrivateKey();

plainText := 'Encrypting and decrypting should be easy!';

// Start with a new RSA object to demonstrate that all we
// need are the keys previously exported:
rsaEncryptor := TChilkatRsa.Create(Self);

// Encrypted output is always binary.  In this case, we want
// to encode the encrypted bytes in a printable string.
// Our choices are "hex", "base64", "url", "quoted-printable".
rsaEncryptor.EncodingMode := 'hex';

// We'll encrypt with the public key and decrypt with the private
// key.  It's also possible to do the reverse.
success := rsaEncryptor.ImportPublicKey(publicKey);

usePrivateKey := 0;
encryptedStr := rsaEncryptor.EncryptStringENC(plainText,usePrivateKey);
Memo1.Lines.Add(encryptedStr);

// Now decrypt:
rsaDecryptor := TChilkatRsa.Create(Self);

rsaDecryptor.EncodingMode := 'hex';
success := rsaDecryptor.ImportPrivateKey(privateKey);

usePrivateKey := 1;
decryptedStr := rsaDecryptor.DecryptStringENC(encryptedStr,usePrivateKey);

Memo1.Lines.Add(decryptedStr);
end;