(C++) 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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#include <CkZip.h>
#include <CkZipEntry.h>
#include <CkBinData.h>
#include <CkXmlDSig.h>
#include <CkCert.h>
#include <CkPublicKey.h>
#include <CkCrypt2.h>
#include <CkXml.h>

void ChilkatSample(void)
    {
    // 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;
    bool success = zip.OpenZip("qa_data/xml_dsig/offline_paperless_kyc.zip");
    if (success == false) {
        std::cout << zip.lastErrorText() << "\r\n";
        return;
    }

    // The .zip should contain 1 XML file.
    CkZipEntry *entry = zip.GetEntryByIndex(0);
    if (zip.get_LastMethodSuccess() == false) {
        std::cout << zip.lastErrorText() << "\r\n";
        return;
    }

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

    CkBinData bdXml;
    // The XML file will be unzipped into the bdXml object.
    success = entry->UnzipToBd(bdXml);
    if (success == false) {
        std::cout << entry->lastErrorText() << "\r\n";
        delete entry;
        return;
    }

    delete entry;

    // First verify the XML digital signature.
    CkXmlDSig dsig;
    success = dsig.LoadSignatureBd(bdXml);
    if (success != true) {
        std::cout << dsig.lastErrorText() << "\r\n";
        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;
    success = cert.LoadFromFile("qa_data/xml_dsig/uidai_auth_sign_prod_2023.cer");
    if (success != true) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

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

    // The XML in this example contains only 1 signature.
    bool bVerifyReferenceDigests = true;
    bool bVerified = dsig.VerifySignature(bVerifyReferenceDigests);
    if (bVerified == false) {
        std::cout << dsig.lastErrorText() << "\r\n";
        std::cout << "The signature was not valid." << "\r\n";
        return;
    }

    std::cout << "The XML digital signature is valid." << "\r\n";

    // 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;
    crypt.put_HashAlgorithm("sha256");
    crypt.put_EncodingMode("hexlower");

    const char *strToHash = "1234567890Lock@487";
    CkBinData bdHash;
    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++) {
        const char *tmpStr = crypt.hashBdENC(bdHash);
        bdHash.Clear();
        bdHash.AppendString(tmpStr,"utf-8");
    }

    std::cout << "Computed Mobile hash = " << bdHash.getString("utf-8") << "\r\n";

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

    std::cout << "Stored Mobile hash   = " << m_hash << "\r\n";

    // 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++) {
        const char *tmpStr = crypt.hashBdENC(bdHash);
        bdHash.Clear();
        bdHash.AppendString(tmpStr,"utf-8");
    }

    std::cout << "Computed Email hash = " << bdHash.getString("utf-8") << "\r\n";

    const char *e_hash = xml.chilkatPath("UidData|Poi|(e)");
    std::cout << "Stored Email hash   = " << e_hash << "\r\n";
    }