(PowerShell) RSASSA-PSS Sign String to Create Base64 PCKS7 Signature

Signs a string to create a PKCS7 signature in the base64 encoding. The signature algorithm is RSASSA-PSS with SHA256.

Note: This example requires Chilkat v9.5.0.67 or greater.

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

# This example requires the Chilkat Crypt API to have been previously unlocked.
# See Unlock Chilkat Crypt for sample code.

$crypt = New-Object Chilkat.Crypt2

# Get a digital certificate with private key from a .pfx
# (Chilkat has many different ways to provide a cert + private key for siging.
# Using a PFX is just one possible option.)
$pfx = New-Object Chilkat.Pfx
$success = $pfx.LoadPfxFile("qa_data/rsassa-pss/privatekey.pfx","PFX_PASSWORD")
if ($success -ne $true) {
    $($pfx.LastErrorText)
    exit
}

# Get the certificate to be used for signing.
# (The typical case for a PFX is that it contains a cert with an associated private key,
# as well as other certificates in the chain of authentication.  The cert with the private
# key should be in the first position at index 0.)
$cert = $pfx.GetCert(0)
if ($pfx.LastMethodSuccess -ne $true) {
    $($pfx.LastErrorText)
    exit
}

$crypt.SetSigningCert($cert)

# Indicate that RSASSA-PSS with SHA256 should be used.
$crypt.SigningAlg = "pss"
$crypt.HashAlgorithm = "sha256"

$crypt.EncodingMode = "base64"

# Sign a string and return the base64 PKCS7 detached signature
$originalText = "This is a test"
$pkcs7sig = $crypt.SignStringENC($originalText)
$("Detached Signature:")
$($pkcs7sig)

# This signature looks like this:
# MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBgl .. YToLqEwTdU87ox5g7rvw==

# The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
# then copy-and-paste the Base64 signature into the form and decode..

# The signature can be verified against the original data like this:
$success = $crypt.VerifyStringENC($originalText,$pkcs7sig)
$("Signature verified: " + $success)
$success = $crypt.VerifyStringENC("Not the original text",$pkcs7sig)
$("Signature verified: " + $success)

# Now we'll create an opaque signature (the opposite of a detached signature). 
# An opaque signature is a PKCS7 message that contains both the original data and
# the signature.  The verification process extracts the original data.
$opaqueSig = $crypt.OpaqueSignStringENC($originalText)
$("Opaque Signature:")
$($opaqueSig)

# The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
# then copy-and-paste the Base64 signature into the form and decode..

# We can verify and extract the original data:
$origTxt = $crypt.OpaqueVerifyStringENC($opaqueSig)
if ($crypt.LastMethodSuccess -ne $true) {
    $("Signature verification failed.")
    $($crypt.LastErrorText)

    exit
}

$("Signature verified.")
$("Extracted text:" + $origTxt)