Create PKCS7 Signature using .cer and .key Files

Uses a digital certificate (.cer file) and private key file to create a PKCS7 signature.

Download: Chilkat .NET Assemblies

'  First, load the .cer and .key files into Chilkat objects...
Dim cert As New Chilkat.Cert()

Dim success As Boolean
success = cert.LoadFromFile("myCert.cer")
If (success <> true) Then
    TextBox1.Text = TextBox1.Text & cert.LastErrorText & vbCrLf
    Exit Sub
End If


Dim privKey As New Chilkat.PrivateKey()
Dim password As String
password = "myPassword"
'  The private key object provides different methods for
'  loading keys of many different formats.
'  This example loads a PKCS8 encrypted private key.
success = privKey.LoadPkcs8EncryptedFile("myPrivateKey.key",password)
If (success <> true) Then
    TextBox1.Text = TextBox1.Text & privKey.LastErrorText & vbCrLf
    Exit Sub
End If


'  NOTE:  In this example, the .cer should contain the public key
'  that corresponds to the private key.


Dim crypt As New Chilkat.Crypt2()

'  Any string argument automatically begins the 30-day trial.
success = crypt.UnlockComponent("30-day trial")
If (success <> true) Then
    TextBox1.Text = TextBox1.Text & crypt.LastErrorText & vbCrLf
    Exit Sub
End If


'  Set the certifcate + private key to be used for signing:
crypt.SetSigningCert2(cert,privKey)

Dim pkcs7Sig() As Byte

Dim textToSign As String
textToSign = "This is the text to be signed."
pkcs7Sig = crypt.SignString(textToSign)
If (pkcs7Sig.Length = 0 ) Then
    TextBox1.Text = TextBox1.Text & crypt.LastErrorText & vbCrLf
    Exit Sub
End If



'  Save the PKCS7 signature to a file.
System.IO.File.WriteAllBytes("sig.p7s", pkcs7Sig)