Delphi DLL

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 DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Asn, Prng, BinData, PrivateKey, Xml, Crypt2, Ecc;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
crypt: HCkCrypt2;
hash1: PWideChar;
privKey: HCkPrivateKey;
prng: HCkPrng;
ecdsa: HCkEcc;
ecdsaSigBase64: PWideChar;
asn: HCkAsn;
xml: HCkXml;
bd: HCkBinData;
r: PWideChar;
s: PWideChar;

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.

crypt := CkCrypt2_Create();
CkCrypt2_putHashAlgorithm(crypt,'SHA256');
CkCrypt2_putCharset(crypt,'utf-8');
CkCrypt2_putEncodingMode(crypt,'base64');

// Hash a string.
hash1 := CkCrypt2__hashStringENC(crypt,'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 := CkPrivateKey_Create();
success := CkPrivateKey_LoadPemFile(privKey,'qa_data/ecc/secp256r1-key-pkcs8.pem');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkPrivateKey__lastErrorText(privKey));
    Exit;
  end;

// Sign the hash..
prng := CkPrng_Create();
ecdsa := CkEcc_Create();
ecdsaSigBase64 := CkEcc__signHashENC(ecdsa,hash1,'base64',privKey,prng);
if (CkEcc_getLastMethodSuccess(ecdsa) <> True) then
  begin
    Memo1.Lines.Add(CkEcc__lastErrorText(ecdsa));
    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 := CkAsn_Create();
success := CkAsn_LoadEncoded(asn,ecdsaSigBase64,'base64');
if (success = False) then
  begin
    Memo1.Lines.Add(CkAsn__lastErrorText(asn));
    Exit;
  end;

// The R and X will be in hexidecimal in the XML.
xml := CkXml_Create();
CkXml_LoadXml(xml,CkAsn__asnToXml(asn));
Memo1.Lines.Add(CkXml__getXml(xml));

// 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 := CkBinData_Create();
r := CkXml__getChildContent(xml,'int[0]');
s := CkXml__getChildContent(xml,'int[1]');
CkBinData_AppendEncoded(bd,r,'hex');
CkBinData_AppendEncoded(bd,s,'hex');

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

CkCrypt2_Dispose(crypt);
CkPrivateKey_Dispose(privKey);
CkPrng_Dispose(prng);
CkEcc_Dispose(ecdsa);
CkAsn_Dispose(asn);
CkXml_Dispose(xml);
CkBinData_Dispose(bd);

end;