(Delphi DLL) RSA Sign Binary Data and Verify (Recover the Original Data)

Demonstrates how to RSA sign binary data and then verify/recover the original data.

Note: This example uses methods introduced in Chilkat v9.5.0.77.

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, BinData, PrivateKey, Rsa, PublicKey;

...

procedure TForm1.Button1Click(Sender: TObject);
var
privKey: HCkPrivateKey;
success: Boolean;
rsa: HCkRsa;
originalData: PWideChar;
bd: HCkBinData;
pubKey: HCkPublicKey;
rsa2: HCkRsa;
bVerified: Boolean;

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

// Load an RSA private key for signing.
privKey := CkPrivateKey_Create();
success := CkPrivateKey_LoadEncryptedPemFile(privKey,'qa_data/pem/rsa_passwd.pem','passwd');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkPrivateKey__lastErrorText(privKey));
    Exit;
  end;

rsa := CkRsa_Create();
CkRsa_ImportPrivateKeyObj(rsa,privKey);

// We have some binary data (in hex) to sign
originalData := '0102030405060708090A';
bd := CkBinData_Create();
CkBinData_AppendEncoded(bd,originalData,'hex');

// If successful, the contents of bd are replaced with the RSA signature.
success := CkRsa_OpenSslSignBd(rsa,bd);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

// Show the RSA signature in base64
Memo1.Lines.Add(CkBinData__getEncoded(bd,'base64'));

// ------------------------------------------
// Get the public key from the private key
pubKey := CkPrivateKey_GetPublicKey(privKey);

// Verify the signature and extract the original data.
rsa2 := CkRsa_Create();
CkRsa_ImportPublicKeyObj(rsa2,pubKey);

bVerified := CkRsa_OpenSslVerifyBd(rsa2,bd);
Memo1.Lines.Add('signature verified: ' + IntToStr(bVerified));

// Show the original data:
Memo1.Lines.Add('original data: ' + CkBinData__getEncoded(bd,'hex'));

CkPublicKey_Dispose(pubKey);

CkPrivateKey_Dispose(privKey);
CkRsa_Dispose(rsa);
CkBinData_Dispose(bd);
CkRsa_Dispose(rsa2);

end;