(Delphi DLL) Aadhaar Paperless Offline e-kyc

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.

For more information, see https://uidai.gov.in/ecosystem/authentication-devices-documents/about-aadhaar-paperless-offline-e-kyc.html

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX 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
zip: HCkZip;
success: Boolean;
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
// 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 := CkZip_GetEntryByIndex(zip,0);
if (CkZip_getLastMethodSuccess(zip) = 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));
    CkZipEntry_Dispose(entry);
    Exit;
  end;

CkZipEntry_Dispose(entry);

// First verify the XML digital signature.
dsig := CkXmlDSig_Create();
success := CkXmlDSig_LoadSignatureBd(dsig,bdXml);
if (success <> True) 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 <> True) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

// Get the certificate's public key.
pubKey := CkCert_ExportPublicKey(cert);
success := CkXmlDSig_SetPublicKey(dsig,pubKey);
CkPublicKey_Dispose(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);
CkBinData_Dispose(bdXml);
CkXmlDSig_Dispose(dsig);
CkCert_Dispose(cert);
CkCrypt2_Dispose(crypt);
CkBinData_Dispose(bdHash);
CkXml_Dispose(xml);

end;