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python.netuuid

Emulate encoding UUID to Base64

I am attempting to emulate the way a C# application converts a UUID to a Base64 value. For some reason, I can get part of the string to match the expected value, but not the whole string.

The C# code I was given:

public static string ToShortGuid(this Guid newGuid) {
string modifiedBase64 = Convert.ToBase64String(newGuid.ToByteArray())
.Replace('+', '-').Replace('/', '_') // avoid invalid URL characters
.Substring(0, 22);
return modifiedBase64;
}

What I have tried in Python 3.6:

import uuid
import base64

encode_str = = base64.urlsafe_b64encode(uuid.UUID("fa190535-6b00-4452-8ab1-319c73082b60").bytes)
print(encode_str)

"fa190535-6b00-4452-8ab1-319c73082b60" is a known UUID, and the application apparently uses the above c# code to generate a 'ShortGuid' value of "NQUZ-gBrUkSKsTGccwgrYA".

When I process the same UUID through my Python code, I get: "-hkFNWsARFKKsTGccwgrYA=="

From both of these output strings, this part matches: "KsTGccwgrYA", but the rest doesn't.

Solution

  • You need to use bytes_le to get the endianness to match Microsoft's:

    base64.urlsafe_b64encode(uuid.UUID("fa190535-6b00-4452-8ab1-319c73082b60").bytes_le)

    That gives b'NQUZ-gBrUkSKsTGccwgrYA=='.