Delphi DLL

Verfies an RSA Signature

See more Apple Keychain Examples

Verifies an RSA signature against the original data. Delphi DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, BinData, Rsa, PublicKey;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
bd: HCkBinData;
i: Integer;
bdSig: HCkBinData;
pubKey: HCkPublicKey;
rsa: HCkRsa;

begin
success := False;

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

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

// Load the signature
bdSig := CkBinData_Create();
success := CkBinData_LoadFile(bdSig,'rsaSignatures/test1.sig');
if (success = False) then
  begin
    Memo1.Lines.Add('Failed to load the RSA signature');
    Exit;
  end;

// Get the public key to be used for signature verification.
pubKey := CkPublicKey_Create();
success := CkPublicKey_LoadFromFile(pubKey,'rsaKeys/chilkat-rsa-2048.pem');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPublicKey__lastErrorText(pubKey));
    Exit;
  end;

rsa := CkRsa_Create();
success := CkRsa_UsePublicKey(rsa,pubKey);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

// 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 := CkRsa_VerifyBd(rsa,bd,'sha256',bdSig);

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

CkBinData_Dispose(bd);
CkBinData_Dispose(bdSig);
CkPublicKey_Dispose(pubKey);
CkRsa_Dispose(rsa);

end;