PowerShell script to hash files. Can accept pipeline input to hash multiple files into one hash. e,g, dir *.dll | Hash.ps1

Hash.ps1

[CmdletBinding()]
Param(
    [Parameter(Mandatory=$True,ValueFromPipelineByPropertyName=$True,ValueFromPipeline=$True,Position=0)]
    [Alias("PSPath","FullName")]
    [String[]]$Path,
    [int]$BufferSize = 65535
)
Begin {
    $buffer = New-Object byte[] $BufferSize 
    $md5 = New-Object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider
}
Process {
    $fs = [IO.File]::OpenRead($Path)
    try {
        $size = $fs.Read($buffer, 0, $BufferSize)
        while ($size -eq $BufferSize)
        {
            $md5.TransformBlock($buffer, 0, $size, $buffer, 0) | out-null
            $size = $fs.Read($buffer, 0, $BufferSize)
        }
        $md5.TransformBlock($buffer, 0, $size, $buffer, 0) | out-null
    }
    finally {
        $fs.Dispose() | out-null
    }
}
End {
    $md5.TransformFinalBlock((New-Object byte[] 0), 0, 0);
    $hash = [BitConverter]::ToString($md5.Hash).Replace("-", "").ToLower();
    $md5.Dispose()
    $hash
}