(Xojo Plugin) 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.

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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 New 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.

Dim cert As New Chilkat.Cert

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

Dim success As Boolean
success = cert.LoadFromSmartcard("")
If (success <> True) Then
    System.DebugLog(cert.LastErrorText)
    Return
End If

// Tell it to use the cert and private key we've loaded.
success = crypt.SetSigningCert(cert)
If (success <> True) Then
    System.DebugLog(crypt.LastErrorText)
    Return
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:
Dim originalData As String
originalData = "This is the string to be signed."
Dim opaqueSig As String
opaqueSig = crypt.OpaqueSignStringENC(originalData)
If (crypt.LastMethodSuccess <> True) Then
    System.DebugLog(crypt.LastErrorText)
    Return
End If

System.DebugLog(opaqueSig)

// 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...

Dim vCrypt As New 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 <> True) Then
    System.DebugLog(vCrypt.LastErrorText)
    Return
End If

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

Dim extractedData As String
extractedData = vCrypt.OpaqueVerifyStringENC(opaqueSig)
If (vCrypt.LastMethodSuccess <> True) Then
    System.DebugLog(vCrypt.LastErrorText)
    Return
End If

System.DebugLog("The extracted data: " + extractedData)

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