Classic ASP

A3/A4 Certificate to Create and Verify an Opaque PKCS7/CMS Signature

Demonstrates how to use an A3 or A4 certificate w/ private key on a smartcard or token to create a PKCS7 opaque signature, and also how to verify an opaque signature.

An opaque signature is different than a detached PKCS7 signature in that it contains the original data. Verifying an opaque signature retrieves the original content.

Chilkat Classic ASP Downloads

Download Chilkat for Classic ASP

Classic ASP

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<%
success = 0

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

set crypt = Server.CreateObject("Chilkat.Crypt2")

' A certificate and private key is needed to create a signature.
' Chilkat provides many different ways to load a certificate and private key, such
' as from a smartcards and hardware tokens, PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
' This example will load the default certificate from the smartcard that is currently in
' the smartcard reader.

set cert = Server.CreateObject("Chilkat.Cert")

' If the smartcard or token requires a PIN, we can set it here to avoid the dialog...
cert.SmartCardPin = "000000"

success = cert.LoadFromSmartcard("")
If (success <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( cert.LastErrorText) & "</pre>"
    Response.End
End If

' Tell it to use the cert and private key we've loaded.
success = crypt.SetSigningCert(cert)
If (success <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( crypt.LastErrorText) & "</pre>"
    Response.End
End If

' Indicate we want the opaque signature in base64 format:
crypt.EncodingMode = "base64"

' Sign the string using the "utf-8" byte representation:
crypt.Charset = "utf-8"

' Create the opaque signature:
originalData = "This is the string to be signed."
opaqueSig = crypt.OpaqueSignStringENC(originalData)
If (crypt.LastMethodSuccess <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( crypt.LastErrorText) & "</pre>"
    Response.End
End If

Response.Write "<pre>" & Server.HTMLEncode( opaqueSig) & "</pre>"

' The output looks like this:
' MIIPgQYJKoZIhvcNAQcCoIIPcjCCD24CAQExCzAJBgUrDgMCGgUAMC8GCSqGSIb3DQEHAaAiBCBUaGlzIGlzIHRoZSBzdHJpbmcgdG8gYmUgc...

' ----------------------------------------------------------------------------------------------
' Now let's verify the signature and retrieve the original data.
' We'll use a new Crypt2 object to keep things completely separate...

set vCrypt = Server.CreateObject("Chilkat.Crypt2")

' We only need the certificate to verify a signature (and extract the data from
' an opaque signature).  The public key is always embedded within a certificate.
success = vCrypt.SetVerifyCert(cert)
If (success <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( vCrypt.LastErrorText) & "</pre>"
    Response.End
End If

vCrypt.EncodingMode = "base64"
vCrypt.Charset = "utf-8"

extractedData = vCrypt.OpaqueVerifyStringENC(opaqueSig)
If (vCrypt.LastMethodSuccess <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( vCrypt.LastErrorText) & "</pre>"
    Response.End
End If

Response.Write "<pre>" & Server.HTMLEncode( "The extracted data: " & extractedData) & "</pre>"

' The output is:
' The extracted data: This is the string to be signed.

%>
</body>
</html>