(Delphi DLL) RSA Encrypt String to Encoded Result and Reverse

See more RSA Examples

Demonstrates how to RSA encrypt a string to a base64 encoded result, and the reverse.

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, PublicKey;

...

procedure TForm1.Button1Click(Sender: TObject);
var
pubKey: HCkPublicKey;
success: Boolean;
rsa: HCkRsa;
encryptedB64: PWideChar;
privKey: HCkPrivateKey;
password: PWideChar;
originalText: PWideChar;

begin
// The RSA public key is used for encryption, and the private key for decryption.

// The public key's role is to make encryption accessible to anyone while ensuring that
// only the private key holder can decrypt the messages.
// The public key is designed to be widely distributed so anyone can use it to encrypt messages
// intended for the owner of the private key.

// Load our 2048-bit RSA public key.
pubKey := CkPublicKey_Create();
// In all Chilkat methods expecting a path, you pass either absolute or relative paths.
success := CkPublicKey_LoadFromFile(pubKey,'rsaKeys/myTestRsaPublic.pem');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPublicKey__lastErrorText(pubKey));
    Exit;
  end;

rsa := CkRsa_Create();

// Tell RSA to use the public key.
CkRsa_ImportPublicKeyObj(rsa,pubKey);

// RSA encryption is for small amounts of data, on the order of 200 bytes or less.
// The maximum number of bytes that can be RSA encrypted depends
// on the RSA key size and padding scheme (OAEP padding vs PKCS#1 v1.5 padding).
// For specific limits, see: RSA Encryption Maximum Number of Bytes

// Encrypt the utf-8 byte representation of the string.
CkRsa_putCharset(rsa,'utf-8');
CkRsa_putEncodingMode(rsa,'base64');

// Be Careful when Using non-us-ascii String Literals in Source Code
encryptedB64 := CkRsa__encryptStringENC(rsa,'Élève français dîne à côté d’un café où l’on sert déjà du gâteau au chocolat et des éclairs délicieux',False);

// ------------------------------------------------------------------------------------------------------------------------
// Let's decrypt, which requires the matching private key...

// Load the matching 2048-bit RSA private key.
privKey := CkPrivateKey_Create();
password := 'secret';
success := CkPrivateKey_LoadAnyFormatFile(privKey,'rsaKeys/myTestRsaPrivate.pem',password);
if (success = False) then
  begin
    Memo1.Lines.Add(CkPrivateKey__lastErrorText(privKey));
    Exit;
  end;

// Tell the RSA object to use the private key.
CkRsa_ImportPrivateKeyObj(rsa,privKey);

// Indicate that after decrypting the resultant decrypted bytes contains the utf-8 byte representation of the text.
CkRsa_putCharset(rsa,'utf-8');
CkRsa_putEncodingMode(rsa,'base64');
originalText := CkRsa__decryptStringENC(rsa,encryptedB64,True);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

Memo1.Lines.Add('Original text = ' + originalText);
Memo1.Lines.Add('Success.');

CkPublicKey_Dispose(pubKey);
CkRsa_Dispose(rsa);
CkPrivateKey_Dispose(privKey);

end;