(PowerShell) Verfies an RSA Signature

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Verifies an RSA signature against the original data.

Chilkat .NET Downloads Chilkat .NET Assemblies

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

# The following data was signed by the following example:
# RSA Sign using a Private Key on a USB Token or Smartcard
$bd = New-Object Chilkat.BinData

for ($i = 0; $i -le 100; $i++) {
    $bd.AppendEncoded("000102030405060708090A0B0C0D0E0F","hex")
}

# Load the signature
$bdSig = New-Object Chilkat.BinData
$success = $bdSig.LoadFile("rsaSignatures/test1.sig")
if ($success -eq $false) {
    $("Failed to load the RSA signature")
    exit
}

# Get the public key to be used for signature verification.
$pubKey = New-Object Chilkat.PublicKey
$success = $pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem")
if ($success -eq $false) {
    $($pubKey.LastErrorText)
    exit
}

$rsa = New-Object Chilkat.Rsa
$rsa.ImportPublicKeyObj($pubKey)

# Verify the hash of the data against the signature.
# We pass in the original data.  Internally, the hash is generated
# and used to validate the signature.
# Validating the RSA signature means two things:  
# (1) the original data is exactly what was signed, and 
# (2) it was signed by the owner of the RSA private key.
$success = $rsa.VerifyBd($bd,"sha256",$bdSig)

if ($success -eq $false) {
    $($rsa.LastErrorText)
    $("Signature invalid.")
}
else {
    $("Signature valid.")
}