(Delphi DLL) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

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, PublicKey, PrivateKey, Rsa, Cert;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
privKey: HCkPrivateKey;
rsa: HCkRsa;
strData: PWideChar;
hexSig: PWideChar;
cert: HCkCert;
pubKey: HCkPublicKey;
rsa2: HCkRsa;

begin
success := False;

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

privKey := CkPrivateKey_Create();

// Load the private key from an RSA PEM file:
success := CkPrivateKey_LoadAnyFormatFile(privKey,'raul_privateKey.key','a0123456789');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPrivateKey__lastErrorText(privKey));
    Exit;
  end;

rsa := CkRsa_Create();

// Import the private key into the RSA component:
success := CkRsa_UsePrivateKey(rsa,privKey);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

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

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

// Sign the string using the sha256 hash algorithm.
// Other valid choices are sha1, sha384, sha512 and others.
hexSig := CkRsa__signStringENC(rsa,strData,'sha256');
if (CkRsa_getLastMethodSuccess(rsa) = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

Memo1.Lines.Add(hexSig);

// Now verify with the public key.
// This example shows how to use the public key from 
// a digital certificate (.cer file)
cert := CkCert_Create();
success := CkCert_LoadFromFile(cert,'raul_publicKey.cer');
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

pubKey := CkPublicKey_Create();
CkCert_GetPublicKey(cert,pubKey);

rsa2 := CkRsa_Create();
success := CkRsa_UsePublicKey(rsa2,pubKey);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa2));
    Exit;
  end;

// Verify the signature against the original data:
CkRsa_putEncodingMode(rsa2,'hex');
success := CkRsa_VerifyStringENC(rsa2,strData,'sha256',hexSig);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa2));
    Exit;
  end;

Memo1.Lines.Add('Signature verified!');

// Verify with incorrect data:
success := CkRsa_VerifyStringENC(rsa2,'something else','sha256',hexSig);
if (success <> True) then
  begin
    Memo1.Lines.Add('Signature not verified! (which was expected in this case)');
  end
else
  begin
    Memo1.Lines.Add('Hmmm... that''s not right...');
  end;

CkPrivateKey_Dispose(privKey);
CkRsa_Dispose(rsa);
CkCert_Dispose(cert);
CkPublicKey_Dispose(pubKey);
CkRsa_Dispose(rsa2);

end;