(Excel) Create P7M Using Pre-Installed Windows Certificate

Demonstrates how to sign a file creating a .p7m file as output. The .p7m contains the signed contents of the original file. It can be verified and restored by calling VerifyP7M.

This example is for Windows only. It automatically searches and locates the desired certificate in the Current User or Local Machine certificate stores. (The certificate must have been pre-installed on the Windows machine, and it must have the private key available. The private key can be located on a USB Authentication Token / Smart Card. If so, then Chilkat *should* automatically use the private key located on the device.)

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

Dim crypt As Chilkat.Crypt2
Set crypt = Chilkat.NewCrypt2


certSubjectCN = "Matt"

Dim cert As Chilkat.Cert
Set cert = Chilkat.NewCert

' Locate and load the certificate by the common name (subject CN).
' This searches the Windows registry-based Current User and Local Machine
' certificate stores for the certificate.  

success = cert.LoadByCommonName(certSubjectCN)
If (success <> True) Then
    Debug.Print "Failed to find certificate."
    Exit Sub
End If

' Make sure a private key is available.
If (cert.HasPrivateKey() <> True) Then
    Debug.Print "This certificate does not have a private key located in the Windows protected store, or on a USB device."
    Exit Sub
End If

' Specify the cert (and implicitly the private key) to be used for signing.
success = crypt.SetSigningCert(cert)

' We can sign any type of file, creating a .p7m as output:

inFile = "qa_data/pdf/fishing.pdf"

outputFile = "qa_output/fishing.pdf.p7m"
success = crypt.CreateP7M(inFile,outputFile)
If (success <> True) Then
    Debug.Print crypt.LastErrorText
    Exit Sub
End If

' Verify and restore the original file:
success = crypt.SetVerifyCert(cert)

inFile = outputFile
outputFile = "qa_output/restored.pdf"

success = crypt.VerifyP7M(inFile,outputFile)
If (success = False) Then
    Debug.Print crypt.LastErrorText
    Exit Sub
End If

Debug.Print "Success!"