VB.NET Requires Chilkat v11.0.0+

Decrypt S/MIME and Verify S/MIME Signatures

See more MIME Examples

_LANGUAGE_ example to decrypt S/MIME and verify S/MIME signatures. The S/MIME is unwrapped to get the original MIME prior to signing/encrypting. VB.NET

Dim success As Boolean = False

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

Dim mime As New Chilkat.Mime

'  Load an S/MIME message from a file:
success = mime.LoadMimeFile("signedMime.txt")
If (success = False) Then
    Debug.WriteLine(mime.LastErrorText)
    Exit Sub
End If


'  The ContainsEncryptedParts/ContainsSignedParts methods
'  can be called to determine if the MIME is encrypted and/or signed:
Dim isEncrypted As Boolean = mime.ContainsEncryptedParts()
Dim isSigned As Boolean = mime.ContainsSignedParts()

'  We don't want the "unwrap extras".  You'll see what those
'  are in a few moments...
mime.UnwrapExtras = False

'  To verify the signature, call UnwrapSecurity.  This will
'  verify the signature(s) and decrypt the S/MIME and restore
'  the MIME to the unsigned/unencrypted state.
'  The results of what was found are present in the MIME object's
'  properties, as well as extra header fields that are added
'  to the unwrapped MIME.
success = mime.UnwrapSecurity()
If (success <> True) Then
    '  UnwrapSecurity returns True if all signatures were
    '  verified and all parts decrypted.
    Debug.WriteLine(mime.LastErrorText)
    Exit Sub
End If


'  The mime.UnwrapExtras property controls whether or not
'  these additional fields are added to the unwrapped MIME:
'  
'  X-NumPartsSigned: 1
'  X-SignaturesValid: yes
'  X-NumPartsEncrypted: 1
'  X-Decrypted: no
'  
'  The X-NumPartsSigned/X-SignaturesValid headers are added
'  if the MIME was signed.  
'  
'  The X-NumPartsEncrypted/X-Decrypted headers are added
'  if the MIME was encrypted.
'  

'  If the MIME was signed, get the certificate used for signing.
If (isSigned = True) Then
    Dim signerCert As New Chilkat.Cert

    '  The NumSignerCerts property indicates how many certificates
    '  were used for signing.  This example will assume the value is 1.
    '  To get the 1st signer cert, call LastSignerCert with an index of 0:
    success = mime.LastSignerCert(0,signerCert)
    If (success = True) Then
        Debug.WriteLine("**** Signer Cert: " & signerCert.SubjectCN)
    End If

End If


'  If the MIME was encrypted, get the certificate used for decryption
If (isEncrypted = True) Then
    '  The NumDecryptCerts property indicates how many certificates
    '  were used for decrypting.  This example will assume the value is 1.
    '  To get the 1st decrypt cert, call LastDecryptCert with an index of 0:
    Dim decryptCert As New Chilkat.Cert
    success = mime.LastDecryptCert(0,decryptCert)
    If (success = True) Then
        Debug.WriteLine("**** Decrypt Cert: " & decryptCert.SubjectCN)
    End If

End If


'  Display the unwrapped MIME:
Debug.WriteLine(mime.GetMime())

'  Save the unwrapped MIME to a file:
success = mime.SaveMime("unwrappedMime.txt")