Generate RSA Key and Sign a String

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.

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;
strData: String;
hexSig: String;

begin
rsa := TChilkatRsa.Create(Self);

//  Any string argument automatically begins the 30-day trial.
success := rsa.UnlockComponent('30-day trial');
if (success <> 1) then
  begin
    ShowMessage('RSA component unlock failed');

  end;

//  Generate a 1024-bit RSA key pair.
rsa.GenerateKey(1024);

//  This example will sign a string, and receive the signature
//  in a hex-encoded string.  Therefore, set the encoding mode
//  to "hex":
rsa.EncodingMode := 'hex';

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

//  Sign the string using the  md5 hash algorithm.
//  Other valid choices are "md2" and "sha-1".
hexSig := rsa.SignStringENC(strData,'md5');

Memo1.Lines.Add(hexSig);
Memo1.Lines.Add(rsa.LastErrorText);

//  Now verify the signature:
success := rsa.VerifyStringENC(strData,'md5',hexSig);
if (success = 1) then
  begin
    ShowMessage('Signature verified!');
  end
else
  begin
    Memo1.Lines.Add(rsa.LastErrorText);
  end;

//  Try it with an invalid signature:
success := rsa.VerifyStringENC(strData,'md5','not a valid sig');
if (success = 1) then
  begin
    ShowMessage('Signature verified!');
  end
else
  begin
    Memo1.Lines.Add(rsa.LastErrorText);
  end;

//  Try it with invalid data:
success := rsa.VerifyStringENC('Not the original data','md5',hexSig);
if (success = 1) then
  begin
    ShowMessage('Signature verified!');
  end
else
  begin
    Memo1.Lines.Add(rsa.LastErrorText);
  end;

//  Try it with the wrong hash algorithm:
success := rsa.VerifyStringENC(strData,'sha-1',hexSig);
if (success = 1) then
  begin
    ShowMessage('Signature verified!');
  end
else
  begin
    Memo1.Lines.Add(rsa.LastErrorText);
  end;
end;