How to get an MD5 checksum in PowerShell

Question

I would like to calculate an MD5 checksum of some content. How do I do this in PowerShell?

Answer 1

Here is a one-line-command example with both computing the proper checksum of the file, like you just downloaded, and comparing it with the published checksum of the original.

For instance, I wrote an example for downloadings from the Apache JMeter project. In this case you have:

1. downloaded binary file
2. checksum of the original which is published in file.md5 as one string in the format:

3a84491f10fb7b147101cf3926c4a855 *apache-jmeter-4.0.zip

Then using this PowerShell command, you can verify the integrity of the downloaded file:

PS C:\Distr> (Get-FileHash .\apache-jmeter-4.0.zip -Algorithm MD5).Hash -eq (Get-Content .\apache-jmeter-4.0.zip.md5 | Convert-String -Example "hash path=hash")

Output:

True

Explanation:

The first operand of -eq operator is a result of computing the checksum for the file:

(Get-FileHash .\apache-jmeter-4.0.zip -Algorithm MD5).Hash

The second operand is the published checksum value. We firstly get content of the file.md5 which is one string and then we extract the hash value based on the string format:

Get-Content .\apache-jmeter-4.0.zip.md5 | Convert-String -Example "hash path=hash"

Both file and file.md5 must be in the same folder for this command work.

Answer 2

This site has an example: Using Powershell for MD5 Checksums. It uses the .NET framework to instantiate an instance of the MD5 hash algorithm to calculate the hash.

Here's the code from the article, incorporating Stephen's comment:

param
(
  $file
)

$algo = [System.Security.Cryptography.HashAlgorithm]::Create("MD5")
$stream = New-Object System.IO.FileStream($Path, [System.IO.FileMode]::Open,
    [System.IO.FileAccess]::Read)

$md5StringBuilder = New-Object System.Text.StringBuilder
$algo.ComputeHash($stream) | % { [void] $md5StringBuilder.Append($_.ToString("x2")) }
$md5StringBuilder.ToString()

$stream.Dispose()

Answer 3

Here is the snippet that I am using to get the MD5 for a given string:

$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")}) 

Answer 4

If you are using the PowerShell Community Extensions there is a Get-Hash commandlet that will do this easily:

C:\PS> "hello world" | Get-Hash -Algorithm MD5


Algorithm: MD5


Path       :
HashString : E42B054623B3799CB71F0883900F2764

Answer 5

Another built-in command that's long been installed in Windows by default dating back to 2003 is Certutil, which of course can be invoked from PowerShell, too.

CertUtil -hashfile file.foo MD5

(Caveat: MD5 should be in all caps for maximum robustness)

Answer 6

As stated in the accepted answer, Get-FileHash is easy to use with files, but it is also possible to use it with strings:

$s = "asdf"
Get-FileHash -InputStream ([System.IO.MemoryStream]::New([System.Text.Encoding]::ASCII.GetBytes($s)))