decrypt.ps1

function Decrypt {
Param ( [Parameter(Position = 0, Mandatory = $True)] [String] $Cpassword )
    function Decrypt-Password {    
        try {
            $Pad = "=" * (4 - ($Cpassword.length % 4))
            $Base64Decoded = [Convert]::FromBase64String($Cpassword + $Pad)
            $AesObject = New-Object System.Security.Cryptography.AesCryptoServiceProvider
            [Byte[]] $AesKey = @(0x4e,0x99,0x06,0xe8,0xfc,0xb6,0x6c,0xc9,0xfa,0xf4,0x93,0x10,0x62,0x0f,0xfe,0xe8,
                                 0xf4,0x96,0xe8,0x06,0xcc,0x05,0x79,0x90,0x20,0x9b,0x09,0xa4,0x33,0xb6,0x6c,0x1b)
            #Set IV to all nulls (thanks Matt) to prevent dynamic generation of IV value
            $AesIV = New-Object Byte[]($AesObject.IV.Length)
            $AesObject.IV = $AesIV
            $AesObject.Key = $AesKey
            $DecryptorObject = $AesObject.CreateDecryptor()
            [Byte[]] $OutBlock = $DecryptorObject.TransformFinalBlock($Base64Decoded, 0, $Base64Decoded.length)
            return [System.Text.UnicodeEncoding]::Unicode.GetString($OutBlock)
        } catch { Write-Error "Failed" }
     
    }
    return Decrypt-Password
}