PowerShell function to compute hashes of string values. Use built-in Get-FileHash for hashing the contents of files.

Get-Hash.ps1

function Get-Hash {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory, ValueFromPipeline)]
        [string]$Value,

        [Parameter()]
        [ValidateSet('sha1', 'sha256', 'sha384', 'sha512', 'md5')]
        [string]$Algorithm = 'sha256',

        [Parameter()]
        [ValidateSet('hex', 'base64')]
        [string]$Format = 'hex'
    )

    $hasher = [System.Security.Cryptography.HashAlgorithm]::Create($Algorithm) 
    $bytes = $hasher.ComputeHash([System.Text.Encoding]::UTF8.GetBytes($Value))

    switch ($Format) {
        "hex" { 
            [System.BitConverter]::ToString($bytes).Replace('-', '').ToLowerInvariant()
        }
        "base64" {
            [System.Convert]::ToBase64String($bytes)
        }
        Default {
            [System.BitConverter]::ToString($bytes).Replace('-', '').ToLowerInvariant()
        }
    }
}