(PowerShell) 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 .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

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

$crypt = New-Object 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

$cert = New-Object Chilkat.Cert
# The LoadFromFile method will automatically detect the format and load it.
$success = $cert.LoadFromFile("qa_data/certs/test_12345678a.cer")
if ($success -ne $true) {
    $($cert.LastErrorText)
    exit
}

# 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..
$privKey = New-Object Chilkat.PrivateKey
$password = "12345678a"
$success = $privKey.LoadPkcs8EncryptedFile("qa_data/certs/test_12345678a.key",$password)
if ($success -ne $true) {
    $($privKey.LastErrorText)
    exit
}

# Set properties required for signing.

# Tell it to use the cert and private key we've loaded.
$success = $crypt.SetSigningCert2($cert,$privKey)
if ($success -ne $true) {
    $($crypt.LastErrorText)
    exit
}

# 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 -ne $true) {
    $($crypt.LastErrorText)
    exit
}

$($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...

$vCrypt = New-Object Chilkat.Crypt2

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

$extractedData = $vCrypt.OpaqueVerifyStringENC($opaqueSig)
if ($vCrypt.LastMethodSuccess -ne $true) {
    $($vCrypt.LastErrorText)
    exit
}

$("The extracted data: " + $extractedData)

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