Pascal (Lazarus/Delphi)

Create ECSDA Signature using Raw r and s Format (not ASN.1)

See more ECC Examples

Demonstrates how to create an ECDSA signature using the raw r/s format.

ECDSA signatures have two equal sized parts, r and s. There are two common formats for encoding the signature:

(a) Concatenating the raw byte array of r and s
(b) Encoding both into a structured ASN.1 / DER sequence.

This example demonstrates how to create a signature that is a byte array of r and s concatenated.

Note: This example requires Chilkat v9.5.0.97 or greater.

Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.StringBuilder,
  Chilkat.PrivateKey,
  Chilkat.Prng,
  Chilkat.Ecc,
  Chilkat.PublicKey;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  sb: TStringBuilder;
  hash: string;
  privKey: TPrivateKey;
  prng: TPrng;
  ecdsa: TEcc;
  ecdsaSigBase64: string;
  pubKey: TPublicKey;
  result: Integer;

begin
  success := False;

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

  //  To create an ECDSA signature, the data first needs to be hashed.  Then the hash
  //  is signed.

  sb := TStringBuilder.Create;
  sb.Append('The quick brown fox jumps over the lazy dog');
  hash := sb.GetHash('sha256','base64','utf-8');

  //  Load the ECDSA key to be used for signing.
  privKey := TPrivateKey.Create;
  success := privKey.LoadPemFile('qa_data/ecc/secp256r1-key-pkcs8.pem');
  if (success <> True) then
    begin
      WriteLn(privKey.LastErrorText);
      Exit;
    end;

  prng := TPrng.Create;
  ecdsa := TEcc.Create;

  //  Produce a signature that is not ASN.1, but is instead the concatenation
  //  of the raw r and s signature parts.
  //  This feature was added in Chilkat v9.5.0.97
  ecdsa.AsnFormat := False;

  ecdsaSigBase64 := ecdsa.SignHashENC(hash,'base64',privKey,prng);
  if (ecdsa.LastMethodSuccess <> True) then
    begin
      WriteLn(ecdsa.LastErrorText);
      Exit;
    end;

  WriteLn('ECDSA signature = ' + ecdsaSigBase64);

  //  -----------------------------------------------------------
  //  Now let's verify the signature using the public key.

  pubKey := TPublicKey.Create;
  success := pubKey.LoadFromFile('qa_data/ecc/secp256r1-pubkey.pem');
  if (success <> True) then
    begin
      WriteLn(pubKey.LastErrorText);
      Exit;
    end;

  //  Note: When verifying, Chilkat will auto-detect the format for both kinds of ECDSA signatures (ASN.1 or binary r+s)
  result := ecdsa.VerifyHashENC(hash,ecdsaSigBase64,'base64',pubKey);
  if (result = 1) then
    begin
      WriteLn('Signature is valid.');
      Exit;
    end;
  if (result = 0) then
    begin
      WriteLn('Signature is invalid.');
      Exit;
    end;
  if (result < 0) then
    begin
      WriteLn(ecdsa.LastErrorText);
      WriteLn('The VerifyHashENC method call failed.');
      Exit;
    end;


  sb.Free;
  privKey.Free;
  prng.Free;
  ecdsa.Free;
  pubKey.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.