(Delphi DLL) Verfies an RSA Signature

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Note: This example requires Chilkat v11.0.0 or greater.

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, 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();
CkRsa_UsePublicKey(rsa,pubKey);

// 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;