Delphi ActiveX

ECDSA Sign Data and Get Raw R and S Values

See more ECC Examples

Demonstrates getting the raw R and S value of an ECDSA signature. 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;
crypt: TChilkatCrypt2;
hash1: WideString;
privKey: TPrivateKey;
prng: TChilkatPrng;
ecdsa: TChilkatEcc;
ecdsaSigBase64: WideString;
asn: TChilkatAsn;
xml: TChilkatXml;
bd: TChilkatBinData;
r: WideString;
s: WideString;

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.

crypt := TChilkatCrypt2.Create(Self);
crypt.HashAlgorithm := 'SHA256';
crypt.Charset := 'utf-8';
crypt.EncodingMode := 'base64';

// Hash a string.
hash1 := crypt.HashStringENC('The quick brown fox jumps over the lazy dog');
Memo1.Lines.Add('hash1 = ' + hash1);

// -----------------------------------------------------------
// An ECDSA private key is used for signing.  The public key is for signature verification.
// Load our ECC private key.
// Our private key file contains this:

// 	// -----BEGIN PRIVATE KEY-----
// 	MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
// 	72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
// 	a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
// 	-----END PRIVATE KEY-----

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;

// Sign the hash..
prng := TChilkatPrng.Create(Self);
ecdsa := TChilkatEcc.Create(Self);
ecdsaSigBase64 := ecdsa.SignHashENC(hash1,'base64',privKey.ControlInterface,prng.ControlInterface);
if (ecdsa.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(ecdsa.LastErrorText);
    Exit;
  end;

// The ECDSA signature is ASN.1 that contains a sequence of 2 large integers (r and s)
// For example:
// SEQUENCE (2 elem)
//   INTEGER (255 bit) 792134D9B4AD82D5431ED03835A88E2596EB35E5B13054BD9B05A0069281ACC9
//   INTEGER (255 bit) 481E758CC1E3CBF825537EC3D9A2CA627E5FAD1137BBEA65DF38658DCB0A9ED5

Memo1.Lines.Add('Base64 ECDSA signature = ' + ecdsaSigBase64);

// If the raw R and S values are needed, here's how to get them:
asn := TChilkatAsn.Create(Self);
success := asn.LoadEncoded(ecdsaSigBase64,'base64');
if (success = 0) then
  begin
    Memo1.Lines.Add(asn.LastErrorText);
    Exit;
  end;

// The R and X will be in hexidecimal in the XML.
xml := TChilkatXml.Create(Self);
xml.LoadXml(asn.AsnToXml());
Memo1.Lines.Add(xml.GetXml());

// The XML looks like this:
// <sequence>
// <int>792134D9B4AD82D5431ED03835A88E2596EB35E5B13054BD9B05A0069281ACC9</int>
// <int>481E758CC1E3CBF825537EC3D9A2CA627E5FAD1137BBEA65DF38658DCB0A9ED5</int>
// </sequence>

// Copy raw R and S hex values into a Chilkat BinData object.
bd := TChilkatBinData.Create(Self);
r := xml.GetChildContent('int[0]');
s := xml.GetChildContent('int[1]');
bd.AppendEncoded(r,'hex');
bd.AppendEncoded(s,'hex');

Memo1.Lines.Add('Number of bytes in bd: ' + IntToStr(bd.NumBytes));
end;