Delphi ActiveX

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.

Delphi ActiveX

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
success: Integer;
sb: TChilkatStringBuilder;
hash: WideString;
privKey: TPrivateKey;
prng: TChilkatPrng;
ecdsa: TChilkatEcc;
ecdsaSigBase64: WideString;
pubKey: TPublicKey;
result: Integer;

begin
success := 0;

// 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 := TChilkatStringBuilder.Create(Self);
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(Self);
success := privKey.LoadPemFile('qa_data/ecc/secp256r1-key-pkcs8.pem');
if (success <> 1) then
  begin
    Memo1.Lines.Add(privKey.LastErrorText);
    Exit;
  end;

prng := TChilkatPrng.Create(Self);
ecdsa := TChilkatEcc.Create(Self);

// 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 := 0;

ecdsaSigBase64 := ecdsa.SignHashENC(hash,'base64',privKey.ControlInterface,prng.ControlInterface);
if (ecdsa.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(ecdsa.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('ECDSA signature = ' + ecdsaSigBase64);

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

pubKey := TPublicKey.Create(Self);
success := pubKey.LoadFromFile('qa_data/ecc/secp256r1-pubkey.pem');
if (success <> 1) then
  begin
    Memo1.Lines.Add(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.ControlInterface);
if (result = 1) then
  begin
    Memo1.Lines.Add('Signature is valid.');
    Exit;
  end;
if (result = 0) then
  begin
    Memo1.Lines.Add('Signature is invalid.');
    Exit;
  end;
if (result < 0) then
  begin
    Memo1.Lines.Add(ecdsa.LastErrorText);
    Memo1.Lines.Add('The VerifyHashENC method call failed.');
    Exit;
  end;
end;