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Visual Basic 6.0

Get Recipient Certificate Info from Encrypted S/MIME

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Demonstrates GetDecryptCertInfo, which examines an encrypted S/MIME entity and writes the recipient-certificate identifiers into a JsonObject. This reveals which certificate(s) the message was encrypted for, so the correct private key can be located before decrypting.

The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Tip: Code to parse the returned JSON can be generated with Chilkat's online tool at https://tools.chilkat.io/jsonParse.

Background. A CMS/PKCS #7 encrypted message carries recipient identifiers (such as issuer and serial number). Inspecting them lets an application determine, without decrypting, which key it needs.

Chilkat Visual Basic 6.0 Downloads

Visual Basic 6.0
Dim success As Long
success = 0

Dim mime As New ChilkatMime
success = mime.LoadMimeFile("qa_data/encrypted.eml")
If (success = 0) Then
    Debug.Print mime.LastErrorText
    Exit Sub
End If

'  Examine the encrypted entity and write the recipient-certificate identifiers to a JsonObject.
'  This tells you which certificate(s) the message was encrypted for, so you can locate the right
'  private key before attempting to decrypt.
Dim certInfo As New ChilkatJsonObject
success = mime.GetDecryptCertInfo(certInfo)
If (success = 0) Then
    Debug.Print mime.LastErrorText
    Exit Sub
End If

certInfo.EmitCompact = 0
Dim json As String
json = certInfo.Emit()
Debug.Print json
'  JSON parsing code for this result can be generated at Chilkat's online tool:
'  https://tools.chilkat.io/jsonParse