Delphi ActiveX

Generate RSA Key and Sign a String

See more RSA Examples

Demonstrates how to generate a new RSA public/private key pair and use it to generate a signature for a string. The (binary) digital signature is returned as a hexidecimalized string. Delphi ActiveX

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
success: Integer;
rsa: TChilkatRsa;
privKey: TPrivateKey;
strData: WideString;
hexSig: WideString;
pubKey: TPublicKey;

begin
success := 0;

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

rsa := TChilkatRsa.Create(Self);

// Generate a 2048-bit RSA key.
privKey := TPrivateKey.Create(Self);
success := rsa.GenKey(2048,privKey.ControlInterface);

rsa.UsePrivateKey(privKey.ControlInterface);

// Return the signature in hex.
rsa.EncodingMode := 'hex';

strData := 'This is the string to be signed.';

// Sign the SHA256 hash of the string.
hexSig := rsa.SignStringENC(strData,'sha256');

Memo1.Lines.Add(hexSig);

// Now verify the signature:
pubKey := TPublicKey.Create(Self);
privKey.ToPublicKey(pubKey.ControlInterface);
rsa.UsePublicKey(pubKey.ControlInterface);

success := rsa.VerifyStringENC(strData,'sha256',hexSig);
if (success = 1) then
  begin
    Memo1.Lines.Add('Signature verified!');
  end
else
  begin
    Memo1.Lines.Add(rsa.LastErrorText);
  end;

// Try it with an invalid signature:
success := rsa.VerifyStringENC(strData,'sha256','not a valid sig');
if (success = 1) then
  begin
    Memo1.Lines.Add('Signature verified!');
  end
else
  begin
    Memo1.Lines.Add('Signature validation failed!');
  end;

// Try it with invalid data:
success := rsa.VerifyStringENC('Not the original data','sha256',hexSig);
if (success = 1) then
  begin
    Memo1.Lines.Add('Signature verified!');
  end
else
  begin
    Memo1.Lines.Add('Signature validation failed!');
  end;
end;