B4X Requires Chilkat v11.0.0+

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. B4X

Dim success As Boolean = 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".
Dim zip As ChilkatZip
zip.Initialize("zip")
success = zip.OpenZip("qa_data/xml_dsig/offline_paperless_kyc.zip")
If success = False Then
    Log(zip.LastErrorText)
    Return
End If


'  The .zip should contain 1 XML file.
Dim entry As ChilkatZipEntry
entry.Initialize("entry")
success = zip.EntryAt(0, entry)
If success = False Then
    Log(zip.LastErrorText)
    Return
End If


'  To get the contents, we need to specify the Share Phrase.
Dim sharePhrase As String = "Lock@487"
zip.DecryptPassword = sharePhrase

Dim bdXml As ChilkatBinData
bdXml.Initialize
'  The XML file will be unzipped into the bdXml object.
success = entry.UnzipToBd(bdXml)
If success = False Then
    Log(entry.LastErrorText)
    Return
End If


'  First verify the XML digital signature.
Dim dsig As ChilkatXmlDSig
dsig.Initialize
success = dsig.LoadSignatureBd(bdXml)
If success = False Then
    Log(dsig.LastErrorText)
    Return
End If


'  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.
Dim cert As ChilkatCert
cert.Initialize("cert")
success = cert.LoadFromFile("qa_data/xml_dsig/uidai_auth_sign_prod_2023.cer")
If success = False Then
    Log(cert.LastErrorText)
    Return
End If


'  Get the certificate's public key.
Dim pubKey As ChilkatPublicKey
pubKey.Initialize
cert.GetPublicKey(pubKey)

dsig.SetPublicKey(pubKey)

'  The XML in this example contains only 1 signature.
Dim bVerifyReferenceDigests As Boolean = True
Dim bVerified As Boolean = dsig.VerifySignature(bVerifyReferenceDigests)
If bVerified = False Then
    Log(dsig.LastErrorText)
    Log("The signature was not valid.")
    Return
End If


Log("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.

Dim crypt As ChilkatCrypt2
crypt.Initialize("crypt")
crypt.HashAlgorithm = "sha256"
crypt.EncodingMode = "hexlower"

Dim strToHash As String = "1234567890Lock@487"
Dim bdHash As ChilkatBinData
bdHash.Initialize
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"
Dim numTimesToHash As Int = 9
Dim i As Int
For i = 1 To numTimesToHash
    Dim tmpStr As String = crypt.HashBdENC(bdHash)
    bdHash.Clear
    bdHash.AppendString(tmpStr, "utf-8")
Next

Log("Computed Mobile hash = " & bdHash.GetString("utf-8"))

'  Let's get the mobile hash stored in the XML and compare it with our computed hash.
Dim xml As ChilkatXml
xml.Initialize
success = xml.LoadBd(bdXml, True)
Dim m_hash As String = xml.ChilkatPath("UidData|Poi|(m)")

Log("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 To numTimesToHash
    Dim tmpStr As String = crypt.HashBdENC(bdHash)
    bdHash.Clear
    bdHash.AppendString(tmpStr, "utf-8")
Next

Log("Computed Email hash = " & bdHash.GetString("utf-8"))

Dim e_hash As String = xml.ChilkatPath("UidData|Poi|(e)")
Log("Stored Email hash   = " & e_hash)