网上有很多使用ComputeHash()的例子。我的测试显示，在网络连接上运行时速度非常慢。下面的片段对我来说运行得更快，但你的里程可能会有所不同:

$md5 = [System.Security.Cryptography.MD5]::Create("MD5")
$fd = [System.IO.File]::OpenRead($file)
$buf = New-Object byte[] (1024*1024*8) # 8 MB buffer
while (($read_len = $fd.Read($buf,0,$buf.length)) -eq $buf.length){
    $total += $buf.length
    $md5.TransformBlock($buf,$offset,$buf.length,$buf,$offset)
    Write-Progress -Activity "Hashing File" `
       -Status $file -percentComplete ($total/$fd.length * 100)
}

# Finalize the last read
$md5.TransformFinalBlock($buf, 0, $read_len)
$hash = $md5.Hash

# Convert hash bytes to a hexadecimal formatted string
$hash | foreach { $hash_txt += $_.ToString("x2") }
Write-Host $hash_txt

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")}) 

另一个早在2003年就默认安装在Windows中的内置命令是Certutil，当然也可以从PowerShell调用它。

CertUtil -hashfile file.foo MD5

(注意:MD5应该全部大写以获得最大的健壮性)

(
    [System.Security.Cryptography.MD5CryptoServiceProvider]::new().ComputeHash(
        [System.Text.UTF8Encoding]::new().GetBytes($yourText)
    ) `
    | %{ [Convert]::ToString($_, 16) }
) -join ''

$yourText = 'hello'输出5d41402abc4b2a76b9719d911017c592

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")

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