(Delphi DLL) RSA Encrypt and Decrypt Strings

Delphi DLL sample code to RSA public-key encrypt and decrypt strings using public and private 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, Rsa;

...

procedure TForm1.Button1Click(Sender: TObject);
var
rsa: HCkRsa;
success: Boolean;
publicKey: PWideChar;
privateKey: PWideChar;
plainText: PWideChar;
rsaEncryptor: HCkRsa;
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();

// 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 := CkRsa_GenerateKey(rsa,1024);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

// Keys are exported in XML format:
publicKey := CkRsa__exportPublicKey(rsa);
privateKey := CkRsa__exportPrivateKey(rsa);

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 := CkRsa_Create();

// 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".
CkRsa_putEncodingMode(rsaEncryptor,'hex');

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

usePrivateKey := False;
encryptedStr := CkRsa__encryptStringENC(rsaEncryptor,plainText,usePrivateKey);
Memo1.Lines.Add(encryptedStr);

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

CkRsa_putEncodingMode(rsaDecryptor,'hex');
success := CkRsa_ImportPrivateKey(rsaDecryptor,privateKey);

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

Memo1.Lines.Add(decryptedStr);

CkRsa_Dispose(rsa);
CkRsa_Dispose(rsaEncryptor);
CkRsa_Dispose(rsaDecryptor);

end;