S/MIME Decrypt

Download Visual Basic Project Files and Source Code

This Visual Basic sample program shows how to decrypt an x-pkcs7-mime MIME message. The attached content of the unencrypted message (a GIF image in this case) is then saved to a file.

' Loads an encrypted MIME message, unwraps the security envelopes, and determines
' if the decryption was successful.
Private Sub Command1_Click()

        Dim mime As New ChilkatMime

        ' Get a 30-day trial code from http:'www.chilkatsoft.com/register30.asp
        mime.UnlockComponent "UnlockCode"
        mime.LoadMimeFile "encrypted.txt"

        ' Determine if this is an encrypted message or not.
        If (mime.IsEncrypted() = 1) Then
            ListBox1.AddItem "Message is encrypted"
        Else
            ListBox1.AddItem "Message is not encrypted"
        End If

        ' Unwrap the security.
        ' The results are stored within the Mime object and can be queried
        ' afterwards.
        ' The UnwrapSecurity does all decryption and signature validation,
        ' regardless of how complex the MIME message may be.
        Dim decryptSuccess As Long
        decryptSuccess = mime.UnwrapSecurity()
        If (decryptSuccess = 1) Then
            ListBox1.AddItem "Message has been decrypted"
        Else
            ListBox1.AddItem "Message not decrypted"
        End If

        ' Save the decrypted MIME message.
        mime.SaveMime "decrypted.txt"
        ' (You can convert any MIME message to XML too.)
        mime.SaveXml "decrypted.xml"

        ' Get the first encrypting certificate.
        ' In complex cases where the MIME is nested and contains
        ' other encrypted MIME messages, there will be more than
        ' one encrypting certificate.
        Dim cert As ChilkatCert
        Set cert = mime.GetEncryptCert(0)
        ListBox1.AddItem "Encrypted By: " + cert.SubjectDN

        ' This example uses a MIME message that included a GIF attachment.
        ' Save the GIF to a file.
        Dim gifAttachment As ChilkatMime
        Set gifAttachment = mime.GetPart(1)
        gifAttachment.SaveBody "dude.gif"

End Sub

' Relevant keywords: mime type, mime format, mime tool, mime decoder, mime file, mime decode
' mime file, mime protocol, mime rfc, mime header, email mime, mail mime, mime decoding,
' mime attachment, mime reader, mime download, mime converter, mime content type,
' mime message, mime file type, mime html, mime downloads, mime parser, mime pdf, convert mime
' mime encoding, mime version 1.0, mime pic, mime video, mime software, mime viewer,
'
'   content-disposition: attachment; filename="smime.p7m"
'   content-transfer-encoding: base64
'   content-type: application/x-pkcs7-mime;
'       name="smime.p7m"