(Delphi DLL) 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.

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;
strData: PWideChar;
hexSig: PWideChar;

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

rsa := CkRsa_Create();

// Generate a 2048-bit RSA key.
success := CkRsa_GenerateKey(rsa,2048);

// To return the signature in hex.
CkRsa_putEncodingMode(rsa,'hex');

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

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

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

// Now verify the signature:
success := CkRsa_VerifyStringENC(rsa,strData,'sha256',hexSig);
if (success = True) then
  begin
    Memo1.Lines.Add('Signature verified!');
  end
else
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
  end;

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

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

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

CkRsa_Dispose(rsa);

end;