RSA Encrypt and Decrypt Strings

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

Download Chilkat RSA ActiveX

uses
    Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
    Dialogs, StdCtrls,
    CHILKATRSALib_TLB,
    OleCtrls;

...

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

begin
rsa := TChilkatRsa.Create(Self);

success := rsa.UnlockComponent('Anything for 30-day trial');
if (success <> 1) then
  begin
    ShowMessage('RSA component unlock failed');

  end;

//  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
    ShowMessage(rsa.LastErrorText);

  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.
rsaEncryptor.ImportPublicKey(publicKey);

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

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

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

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

Memo1.Lines.Add(decryptedStr);
end;