(Delphi ActiveX) Verfies an RSA Signature

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Verifies an RSA signature against the original data.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

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
bd: TChilkatBinData;
i: Integer;
bdSig: TChilkatBinData;
success: Integer;
pubKey: TPublicKey;
rsa: TChilkatRsa;

begin
// The following data was signed by the following example:
// RSA Sign using a Private Key on a USB Token or Smartcard
bd := TChilkatBinData.Create(Self);

for i := 0 to 100 do
  begin
    bd.AppendEncoded('000102030405060708090A0B0C0D0E0F','hex');
  end;

// Load the signature
bdSig := TChilkatBinData.Create(Self);
success := bdSig.LoadFile('rsaSignatures/test1.sig');
if (success = 0) then
  begin
    Memo1.Lines.Add('Failed to load the RSA signature');
    Exit;
  end;

// Get the public key to be used for signature verification.
pubKey := TPublicKey.Create(Self);
success := pubKey.LoadFromFile('rsaKeys/chilkat-rsa-2048.pem');
if (success = 0) then
  begin
    Memo1.Lines.Add(pubKey.LastErrorText);
    Exit;
  end;

rsa := TChilkatRsa.Create(Self);
rsa.ImportPublicKeyObj(pubKey.ControlInterface);

// Verify the hash of the data against the signature.
// We pass in the original data.  Internally, the hash is generated
// and used to validate the signature.
// Validating the RSA signature means two things:  
// (1) the original data is exactly what was signed, and 
// (2) it was signed by the owner of the RSA private key.
success := rsa.VerifyBd(bd.ControlInterface,'sha256',bdSig.ControlInterface);

if (success = 0) then
  begin
    Memo1.Lines.Add(rsa.LastErrorText);
    Memo1.Lines.Add('Signature invalid.');
  end
else
  begin
    Memo1.Lines.Add('Signature valid.');
  end;
end;