(Visual Basic 6.0) Verify Opaque Signature and Retrieve Signing Certificates

Demonstrates how to verify a PCKS7 opaque digital signature (signed data), extract the original file/data, and then extract the certificate(s) that were used to sign.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim crypt As New ChilkatCrypt2

' Verify a PKCS7 signed-data (opaque signature) file and extract the original content to a file.
Dim success As Long
success = crypt.VerifyP7M("qa_data/p7m/opaqueSig.p7","qa_output/originalData.dat")
If (success <> 1) Then
    Debug.Print crypt.LastErrorText
    Exit Sub
End If

' Alternatively, we can do it in memory...
Dim binData As New ChilkatBinData
success = binData.LoadFile("qa_data/p7m/opaqueSig.p7")
' Your app should check for success, but we'll skip the check for brevity..

' If verified, the signature is unwrapped and binData is replaced with the original data that was signed.
success = crypt.OpaqueVerifyBd(binData)
If (success <> 1) Then
    Debug.Print crypt.LastErrorText
    Exit Sub
End If

' For our testing, we signed some text, so we can get it from the binData..
Debug.Print "Original Data:"
Debug.Print binData.GetString("utf-8")

' After any method call that verifies a signature, the crypt object will contain the certificate(s)
' that were used for signing (assuming the X.509 certs were available in the signature, which is typically the case).

' Get the number of signing certificates, and get each..
Dim numCerts As Long
numCerts = crypt.NumSignerCerts
Dim i As Long
i = 0
Do While i < numCerts
    Dim cert As ChilkatCert
    Set cert = crypt.GetSignerCert(i)
    Debug.Print cert.SubjectDN

    i = i + 1
Loop

' We could also get the complete certificate chain of each signer cert,
' assuming the certs in the chain of authentication to the trusted root
' are available on the system, or provided to Chilkat by some other means
' (such as via the XmlCertVault class, the TrustedRoots class, etc.)
i = 0
Do While i < numCerts
    Dim certChain As ChilkatCertChain
    Set certChain = crypt.GetSignerCertChain(i)
    ' You can examine the various properties and methods for certChain in the online
    ' reference documentation...

    i = i + 1
Loop