下面是一个尝试验证SHA256指纹的漂亮打印示例。我使用PowerShell v4下载了gpg4win v3.0.3(需要Get-FileHash)。

从https://www.gpg4win.org/download.html下载包，打开PowerShell，从下载页面抓取散列，然后运行:

cd ${env:USERPROFILE}\Downloads
$file = "gpg4win-3.0.3.exe"

# Set $hash to the hash reference from the download page:
$hash = "477f56212ee60cc74e0c5e5cc526cec52a069abff485c89c2d57d1b4b6a54971"

# If you have an MD5 hash: # $hashAlgo="MD5"
$hashAlgo = "SHA256"

$computed_hash = (Get-FileHash -Algorithm $hashAlgo $file).Hash.ToUpper()
if ($computed_hash.CompareTo($hash.ToUpper()) -eq 0 ) {
    Write-Output "Hash matches for file $file" 
} 
else { 
    Write-Output ("Hash DOES NOT match for file {0}: `nOriginal hash: {1} `nComputed hash: {2}" -f ($file, $hash.ToUpper(), $computed_hash)) 
}

输出:

Hash matches for file gpg4win-3.0.3.exe

下面是我用来获取给定字符串的MD5的代码片段:

$text = "text goes here..."
$md5  = [Security.Cryptography.MD5CryptoServiceProvider]::new()
$utf8 = [Text.UTF8Encoding]::UTF8
$bytes= $md5.ComputeHash($utf8.GetBytes($text))
$hash = [string]::Concat($bytes.foreach{$_.ToString("x2")}) 

这是我用来获得一致哈希值的方法:

function New-CrcTable {
    [uint32]$c = $null
    $crcTable = New-Object 'System.Uint32[]' 256

    for ($n = 0; $n -lt 256; $n++) {
        $c = [uint32]$n
        for ($k = 0; $k -lt 8; $k++) {
            if ($c -band 1) {
                $c = (0xEDB88320 -bxor ($c -shr 1))
            }
            else {
                $c = ($c -shr 1)
            }
        }
        $crcTable[$n] = $c
    }

    Write-Output $crcTable
}

function Update-Crc ([uint32]$crc, [byte[]]$buffer, [int]$length, $crcTable) {
    [uint32]$c = $crc

    for ($n = 0; $n -lt $length; $n++) {
        $c = ($crcTable[($c -bxor $buffer[$n]) -band 0xFF]) -bxor ($c -shr 8)
    }

    Write-Output $c
}

function Get-CRC32 {
    <#
        .SYNOPSIS
            Calculate CRC.
        .DESCRIPTION
            This function calculates the CRC of the input data using the CRC32 algorithm.
        .EXAMPLE
            Get-CRC32 $data
        .EXAMPLE
            $data | Get-CRC32
        .NOTES
            C to PowerShell conversion based on code in https://www.w3.org/TR/PNG/#D-CRCAppendix

            Author: Øyvind Kallstad
            Date: 06.02.2017
            Version: 1.0
        .INPUTS
            byte[]
        .OUTPUTS
            uint32
        .LINK
            https://communary.net/
        .LINK
            https://www.w3.org/TR/PNG/#D-CRCAppendix

    #>
    [CmdletBinding()]
    param (
        # Array of Bytes to use for CRC calculation
        [Parameter(Position = 0, ValueFromPipeline = $true)]
        [ValidateNotNullOrEmpty()]
        [byte[]]$InputObject
    )

    $dataArray = @()
    $crcTable = New-CrcTable
    foreach ($item  in $InputObject) {
        $dataArray += $item
    }
    $inputLength = $dataArray.Length
    Write-Output ((Update-Crc -crc 0xffffffffL -buffer $dataArray -length $inputLength -crcTable $crcTable) -bxor 0xffffffffL)
}

function GetHash() {
    [CmdletBinding()]
    param(
        [Parameter(Position = 0, ValueFromPipeline = $true)]
        [ValidateNotNullOrEmpty()]
        [string]$InputString
    )

    $bytes = [System.Text.Encoding]::UTF8.GetBytes($InputString)
    $hasCode = Get-CRC32 $bytes
    $hex = "{0:x}" -f $hasCode
    return $hex
}

function Get-FolderHash {
    [CmdletBinding()]
    param(
        [Parameter(Position = 0, ValueFromPipeline = $true)]
        [ValidateNotNullOrEmpty()]
        [string]$FolderPath
    )

    $FolderContent = New-Object System.Collections.ArrayList
    Get-ChildItem $FolderPath -Recurse | Where-Object {
        if ([System.IO.File]::Exists($_)) {
            $FolderContent.AddRange([System.IO.File]::ReadAllBytes($_)) | Out-Null
        }
    }

    $hasCode = Get-CRC32 $FolderContent
    $hex = "{0:x}" -f $hasCode
    return $hex.Substring(0, 8).ToLower()
}

这里有两行，只需在第2行中更改“hello”:

PS C:\> [Reflection.Assembly]::LoadWithPartialName("System.Web")
PS C:\> [System.Web.Security.FormsAuthentication]::HashPasswordForStoringInConfigFile("hello", "MD5")

从PowerShell版本4开始，使用Get-FileHash cmdlet可以很容易地实现文件的开箱即用:

Get-FileHash <filepath> -Algorithm MD5

这当然是更可取的，因为它避免了注释中指出的旧PowerShell解决方案所提供的问题(使用流，关闭它，并支持大文件)。

如果内容是字符串:

$someString = "Hello, World!"
$md5 = New-Object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider
$utf8 = New-Object -TypeName System.Text.UTF8Encoding
$hash = [System.BitConverter]::ToString($md5.ComputeHash($utf8.GetBytes($someString)))

对于较旧的PowerShell版本

如果内容为文件:

$someFilePath = "C:\foo.txt"
$md5 = New-Object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider
$hash = [System.BitConverter]::ToString($md5.ComputeHash([System.IO.File]::ReadAllBytes($someFilePath)))

下面是一个尝试验证SHA256指纹的漂亮打印示例。我使用PowerShell v4下载了gpg4win v3.0.3(需要Get-FileHash)。

从https://www.gpg4win.org/download.html下载包，打开PowerShell，从下载页面抓取散列，然后运行:

cd ${env:USERPROFILE}\Downloads
$file = "gpg4win-3.0.3.exe"

# Set $hash to the hash reference from the download page:
$hash = "477f56212ee60cc74e0c5e5cc526cec52a069abff485c89c2d57d1b4b6a54971"

# If you have an MD5 hash: # $hashAlgo="MD5"
$hashAlgo = "SHA256"

$computed_hash = (Get-FileHash -Algorithm $hashAlgo $file).Hash.ToUpper()
if ($computed_hash.CompareTo($hash.ToUpper()) -eq 0 ) {
    Write-Output "Hash matches for file $file" 
} 
else { 
    Write-Output ("Hash DOES NOT match for file {0}: `nOriginal hash: {1} `nComputed hash: {2}" -f ($file, $hash.ToUpper(), $computed_hash)) 
}

输出:

Hash matches for file gpg4win-3.0.3.exe