(PureBasic) 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 PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkPublicKey.pb"
IncludeFile "CkBinData.pb"
IncludeFile "CkXmlDSig.pb"
IncludeFile "CkZipEntry.pb"
IncludeFile "CkXml.pb"
IncludeFile "CkCrypt2.pb"
IncludeFile "CkZip.pb"
IncludeFile "CkCert.pb"

Procedure ChilkatExample()

    ; 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.i = CkZip::ckCreate()
    If zip.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success.i = CkZip::ckOpenZip(zip,"qa_data/xml_dsig/offline_paperless_kyc.zip")
    If success = 0
        Debug CkZip::ckLastErrorText(zip)
        CkZip::ckDispose(zip)
        ProcedureReturn
    EndIf

    ; The .zip should contain 1 XML file.
    entry.i = CkZip::ckGetEntryByIndex(zip,0)
    If CkZip::ckLastMethodSuccess(zip) = 0
        Debug CkZip::ckLastErrorText(zip)
        CkZip::ckDispose(zip)
        ProcedureReturn
    EndIf

    ; To get the contents, we need to specify the Share Phrase.
    sharePhrase.s = "Lock@487"
    CkZip::setCkDecryptPassword(zip, sharePhrase)

    bdXml.i = CkBinData::ckCreate()
    If bdXml.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; The XML file will be unzipped into the bdXml object.
    success = CkZipEntry::ckUnzipToBd(entry,bdXml)
    If success = 0
        Debug CkZipEntry::ckLastErrorText(entry)
        CkZipEntry::ckDispose(entry)

        CkZip::ckDispose(zip)
        CkBinData::ckDispose(bdXml)
        ProcedureReturn
    EndIf

    CkZipEntry::ckDispose(entry)

    ; First verify the XML digital signature.
    dsig.i = CkXmlDSig::ckCreate()
    If dsig.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkXmlDSig::ckLoadSignatureBd(dsig,bdXml)
    If success <> 1
        Debug CkXmlDSig::ckLastErrorText(dsig)
        CkZip::ckDispose(zip)
        CkBinData::ckDispose(bdXml)
        CkXmlDSig::ckDispose(dsig)
        ProcedureReturn
    EndIf

    ; 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.i = CkCert::ckCreate()
    If cert.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkCert::ckLoadFromFile(cert,"qa_data/xml_dsig/uidai_auth_sign_prod_2023.cer")
    If success <> 1
        Debug CkCert::ckLastErrorText(cert)
        CkZip::ckDispose(zip)
        CkBinData::ckDispose(bdXml)
        CkXmlDSig::ckDispose(dsig)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    ; Get the certificate's public key.
    pubKey.i = CkCert::ckExportPublicKey(cert)
    success = CkXmlDSig::ckSetPublicKey(dsig,pubKey)
    CkPublicKey::ckDispose(pubKey)

    ; The XML in this example contains only 1 signature.
    bVerifyReferenceDigests.i = 1
    bVerified.i = CkXmlDSig::ckVerifySignature(dsig,bVerifyReferenceDigests)
    If bVerified = 0
        Debug CkXmlDSig::ckLastErrorText(dsig)
        Debug "The signature was not valid."
        CkZip::ckDispose(zip)
        CkBinData::ckDispose(bdXml)
        CkXmlDSig::ckDispose(dsig)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    Debug "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.i = CkCrypt2::ckCreate()
    If crypt.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkCrypt2::setCkHashAlgorithm(crypt, "sha256")
    CkCrypt2::setCkEncodingMode(crypt, "hexlower")

    strToHash.s = "1234567890Lock@487"
    bdHash.i = CkBinData::ckCreate()
    If bdHash.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkBinData::ckAppendString(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.i = 9
    i.i
    For i = 1 To numTimesToHash
        tmpStr.s = CkCrypt2::ckHashBdENC(crypt,bdHash)
        CkBinData::ckClear(bdHash)
        CkBinData::ckAppendString(bdHash,tmpStr,"utf-8")
    Next

    Debug "Computed Mobile hash = " + CkBinData::ckGetString(bdHash,"utf-8")

    ; Let's get the mobile hash stored in the XML and compare it with our computed hash.
    xml.i = CkXml::ckCreate()
    If xml.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkXml::ckLoadBd(xml,bdXml,1)
    m_hash.s = CkXml::ckChilkatPath(xml,"UidData|Poi|(m)")

    Debug "Stored Mobile hash   = " + m_hash

    ; Now do the same thing for the email hash:

    strToHash = "abc@gm.comLock@487"
    CkBinData::ckClear(bdHash)
    success = CkBinData::ckAppendString(bdHash,strToHash,"utf-8")

    For i = 1 To numTimesToHash
        tmpStr.s = CkCrypt2::ckHashBdENC(crypt,bdHash)
        CkBinData::ckClear(bdHash)
        CkBinData::ckAppendString(bdHash,tmpStr,"utf-8")
    Next

    Debug "Computed Email hash = " + CkBinData::ckGetString(bdHash,"utf-8")

    e_hash.s = CkXml::ckChilkatPath(xml,"UidData|Poi|(e)")
    Debug "Stored Email hash   = " + e_hash


    CkZip::ckDispose(zip)
    CkBinData::ckDispose(bdXml)
    CkXmlDSig::ckDispose(dsig)
    CkCert::ckDispose(cert)
    CkCrypt2::ckDispose(crypt)
    CkBinData::ckDispose(bdHash)
    CkXml::ckDispose(xml)


    ProcedureReturn
EndProcedure