(Xojo Plugin) Create and Verify an Opaque PKCS7/CMS Signature

Demonstrates how 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 Xojo Plugin Download Xojo Plugin for Windows, Linux, Mac OS X, and ARM, ARM64

// 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 PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
// This example will load the certificate from a .crt and the private key from a .key file

Dim cert As New Chilkat.Cert
// The LoadFromFile method will automatically detect the format and load it.
Dim success As Boolean
success = cert.LoadFromFile("qa_data/certs/test_12345678a.cer")
If (success <> True) Then
    System.DebugLog(cert.LastErrorText)
    Return
End If

// Our private key is in an encrypted PKCS8 format.
// If you don't know the format of your key, but you do know it's encrypted,
// and requires a password, then just call any of the Chilkat methods that load
// a private key w/ a password argument.  Chilkat will auto-detect the format
// and load it correctly even if it's not the format indicated by the method name..
Dim privKey As New Chilkat.PrivateKey
Dim password As String
password = "12345678a"
success = privKey.LoadPkcs8EncryptedFile("qa_data/certs/test_12345678a.key",password)
If (success <> True) Then
    System.DebugLog(privKey.LastErrorText)
    Return
End If

// Set properties required for signing.

// Tell it to use the cert and private key we've loaded.
success = crypt.SetSigningCert2(cert,privKey)
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

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.