Delphi DLL

Aadhaar Paperless Offline e-kyc

See more XML Digital Signatures Examples

Opens an encrypted .zip containing Aadhaar Paperless Offline e-KYC XML. Gets the XML and validates the digital signature. Then computes the hash for the mobile number and Email ID. Delphi DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, XmlDSig, Zip, PublicKey, BinData, ZipEntry, Cert, Crypt2, Xml;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
zip: HCkZip;
entry: HCkZipEntry;
sharePhrase: PWideChar;
bdXml: HCkBinData;
dsig: HCkXmlDSig;
cert: HCkCert;
pubKey: HCkPublicKey;
bVerifyReferenceDigests: Boolean;
bVerified: Boolean;
crypt: HCkCrypt2;
strToHash: PWideChar;
bdHash: HCkBinData;
numTimesToHash: Integer;
i: Integer;
tmpStr: PWideChar;
xml: HCkXml;
m_hash: PWideChar;
tmpStr: PWideChar;
e_hash: PWideChar;

begin
success := False;

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

// Open the .zip containing the Aadhaar Paperless Offline e-KYC XML.
// The .zip is encrypted using the "Share Phrase".
zip := CkZip_Create();
success := CkZip_OpenZip(zip,'qa_data/xml_dsig/offline_paperless_kyc.zip');
if (success = False) then
  begin
    Memo1.Lines.Add(CkZip__lastErrorText(zip));
    Exit;
  end;

// The .zip should contain 1 XML file.
entry := CkZipEntry_Create();
success := CkZip_EntryAt(zip,0,entry);
if (success = False) then
  begin
    Memo1.Lines.Add(CkZip__lastErrorText(zip));
    Exit;
  end;

// To get the contents, we need to specify the Share Phrase.
sharePhrase := 'Lock@487';
CkZip_putDecryptPassword(zip,sharePhrase);

bdXml := CkBinData_Create();
// The XML file will be unzipped into the bdXml object.
success := CkZipEntry_UnzipToBd(entry,bdXml);
if (success = False) then
  begin
    Memo1.Lines.Add(CkZipEntry__lastErrorText(entry));
    Exit;
  end;

// First verify the XML digital signature.
dsig := CkXmlDSig_Create();
success := CkXmlDSig_LoadSignatureBd(dsig,bdXml);
if (success = False) then
  begin
    Memo1.Lines.Add(CkXmlDSig__lastErrorText(dsig));
    Exit;
  end;

// The UIDAI XML signature does not contain the KeyInfo, so we must load the uidai certificate
// and indicate that its public key is to be used for verifying the signature.
cert := CkCert_Create();
success := CkCert_LoadFromFile(cert,'qa_data/xml_dsig/uidai_auth_sign_prod_2023.cer');
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

// Get the certificate's public key.
pubKey := CkPublicKey_Create();
CkCert_GetPublicKey(cert,pubKey);

CkXmlDSig_SetPublicKey(dsig,pubKey);

// The XML in this example contains only 1 signature.
bVerifyReferenceDigests := True;
bVerified := CkXmlDSig_VerifySignature(dsig,bVerifyReferenceDigests);
if (bVerified = False) then
  begin
    Memo1.Lines.Add(CkXmlDSig__lastErrorText(dsig));
    Memo1.Lines.Add('The signature was not valid.');
    Exit;
  end;

Memo1.Lines.Add('The XML digital signature is valid.');

// Let's compute the hash for the Mobile Number.

// 	Hashing logic for Mobile Number :
// 	Sha256(Sha256(Mobile+SharePhrase))*number of times last digit of Aadhaar number
// 	(Ref ID field contains last 4 digits).
// 
// 	Example :
// 	Mobile: 1234567890
// 	Aadhaar Number:XXXX XXXX 3632
// 	Passcode : Lock@487
// 	Hash: Sha256(Sha256(1234567890Lock@487))*2
// 	In case of Aadhaar number ends with Zero we will hashed one time.

crypt := CkCrypt2_Create();
CkCrypt2_putHashAlgorithm(crypt,'sha256');
CkCrypt2_putEncodingMode(crypt,'hexlower');

strToHash := '1234567890Lock@487';
bdHash := CkBinData_Create();
success := CkBinData_AppendString(bdHash,strToHash,'utf-8');

// Hash a number of times equal to the last digit of your Aadhaar number.
// If the Aadhaar number ends with 0, then hash one time.
// For this example, we'll just set the number of times to hash
// for the case where an Aadhaar number ends in "9"
numTimesToHash := 9;

for i := 1 to numTimesToHash do
  begin
    tmpStr := CkCrypt2__hashBdENC(crypt,bdHash);
    CkBinData_Clear(bdHash);
    CkBinData_AppendString(bdHash,tmpStr,'utf-8');
  end;

Memo1.Lines.Add('Computed Mobile hash = ' + CkBinData__getString(bdHash,'utf-8'));

// Let's get the mobile hash stored in the XML and compare it with our computed hash.
xml := CkXml_Create();
success := CkXml_LoadBd(xml,bdXml,True);
m_hash := CkXml__chilkatPath(xml,'UidData|Poi|(m)');

Memo1.Lines.Add('Stored Mobile hash   = ' + m_hash);

// Now do the same thing for the email hash:

strToHash := 'abc@gm.comLock@487';
CkBinData_Clear(bdHash);
success := CkBinData_AppendString(bdHash,strToHash,'utf-8');

for i := 1 to numTimesToHash do
  begin
    tmpStr := CkCrypt2__hashBdENC(crypt,bdHash);
    CkBinData_Clear(bdHash);
    CkBinData_AppendString(bdHash,tmpStr,'utf-8');
  end;

Memo1.Lines.Add('Computed Email hash = ' + CkBinData__getString(bdHash,'utf-8'));

e_hash := CkXml__chilkatPath(xml,'UidData|Poi|(e)');
Memo1.Lines.Add('Stored Email hash   = ' + e_hash);

CkZip_Dispose(zip);
CkZipEntry_Dispose(entry);
CkBinData_Dispose(bdXml);
CkXmlDSig_Dispose(dsig);
CkCert_Dispose(cert);
CkPublicKey_Dispose(pubKey);
CkCrypt2_Dispose(crypt);
CkBinData_Dispose(bdHash);
CkXml_Dispose(xml);

end;