Base64 Encoded SHA256 Hashes

File this away in your “might come in handy some day” drawer… Here’s a quick PowerShell script to calculate the Base64 SHA256 hash of a file:

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param(
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    [Parameter(Mandatory=$True,
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            ValueFromPipeline=$True)]
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    $filePath
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)
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$hasher = [System.Security.Cryptography.SHA256]::Create()
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$content = Get-Content -Encoding byte $filePath
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$hash = [System.Convert]::ToBase64String($hasher.ComputeHash($content))
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Write-Output ($filePath.ToString() + ": " + $hash)

You can pipe every file in a directory to this script like this:

ls -File |% {.\Get-FileHash.ps1 $_}

C#

Or, if you prefer, a C# example:

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using System;
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using System.IO;
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using System.Security.Cryptography;
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static string Base64SHA256(string filePath)
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{
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    var hasher = SHA256.Create();
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    byte[] hashValue;
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    using(Stream s = File.OpenRead(filePath))
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    {
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        hashValue = hasher.ComputeHash(s);
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    }
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    return Convert.ToBase64String(hashValue);
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}

Finally, the same thing in Python. This function is a bit more involved than the other examples because it takes advantage of Python’s dynamic typing. You can pass it a string or any object with a read attribute. Note that this function relies on the path.py module, though you can remove that dependency pretty easily.

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import hashlib, base64
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from path import path
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def calc_sha(obj):
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    """Calculates the base64-encoded SHA hash of a file."""
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    try:
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        pathfile = path(obj)
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    except UnicodeDecodeError:
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        pathfile = None
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    sha = hashlib.sha256()
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    if pathfile and pathfile.exists():
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        return base64.b64encode(pathfile.read_hash('SHA256'))
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    elif isinstance(obj, basestring):
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        sha.update(obj)
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    elif hasattr(obj, 'read'):
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        while True:
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            d = obj.read(8192)
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            if not d:
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                break
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            sha.update(d)
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    else:
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        return None
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    r = sha.digest()
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    r = base64.b64encode(r)
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    return r

This particular implementation can also be found in my propane utility library (in the filetools module).