(Java) 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

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // 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".
    CkZip zip = new CkZip();
    boolean success = zip.OpenZip("qa_data/xml_dsig/offline_paperless_kyc.zip");
    if (success == false) {
        System.out.println(zip.lastErrorText());
        return;
        }

    // The .zip should contain 1 XML file.
    CkZipEntry entry = zip.GetEntryByIndex(0);
    if (zip.get_LastMethodSuccess() == false) {
        System.out.println(zip.lastErrorText());
        return;
        }

    // To get the contents, we need to specify the Share Phrase.
    String sharePhrase = "Lock@487";
    zip.put_DecryptPassword(sharePhrase);

    CkBinData bdXml = new CkBinData();
    // The XML file will be unzipped into the bdXml object.
    success = entry.UnzipToBd(bdXml);
    if (success == false) {
        System.out.println(entry.lastErrorText());

        return;
        }

    // First verify the XML digital signature.
    CkXmlDSig dsig = new CkXmlDSig();
    success = dsig.LoadSignatureBd(bdXml);
    if (success != true) {
        System.out.println(dsig.lastErrorText());
        return;
        }

    // 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.
    CkCert cert = new CkCert();
    success = cert.LoadFromFile("qa_data/xml_dsig/uidai_auth_sign_prod_2023.cer");
    if (success != true) {
        System.out.println(cert.lastErrorText());
        return;
        }

    // Get the certificate's public key.
    CkPublicKey pubKey = cert.ExportPublicKey();
    success = dsig.SetPublicKey(pubKey);

    // The XML in this example contains only 1 signature.
    boolean bVerifyReferenceDigests = true;
    boolean bVerified = dsig.VerifySignature(bVerifyReferenceDigests);
    if (bVerified == false) {
        System.out.println(dsig.lastErrorText());
        System.out.println("The signature was not valid.");
        return;
        }

    System.out.println("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.

    CkCrypt2 crypt = new CkCrypt2();
    crypt.put_HashAlgorithm("sha256");
    crypt.put_EncodingMode("hexlower");

    String strToHash = "1234567890Lock@487";
    CkBinData bdHash = new CkBinData();
    success = bdHash.AppendString(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"
    int numTimesToHash = 9;
    int i;
    for (i = 1; i <= numTimesToHash; i++) {
        String tmpStr = crypt.hashBdENC(bdHash);
        bdHash.Clear();
        bdHash.AppendString(tmpStr,"utf-8");
        }

    System.out.println("Computed Mobile hash = " + bdHash.getString("utf-8"));

    // Let's get the mobile hash stored in the XML and compare it with our computed hash.
    CkXml xml = new CkXml();
    success = xml.LoadBd(bdXml,true);
    String m_hash = xml.chilkatPath("UidData|Poi|(m)");

    System.out.println("Stored Mobile hash   = " + m_hash);

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

    strToHash = "abc@gm.comLock@487";
    bdHash.Clear();
    success = bdHash.AppendString(strToHash,"utf-8");

    for (i = 1; i <= numTimesToHash; i++) {
        String tmpStr = crypt.hashBdENC(bdHash);
        bdHash.Clear();
        bdHash.AppendString(tmpStr,"utf-8");
        }

    System.out.println("Computed Email hash = " + bdHash.getString("utf-8"));

    String e_hash = xml.chilkatPath("UidData|Poi|(e)");
    System.out.println("Stored Email hash   = " + e_hash);
  }
}