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[Solved] Late Nite Numbers Puzzler for Nerds (hexbear.net)

submitted 3 months ago* (last edited 3 months ago) by [email protected] to c/[email protected]

2 comments fedilink hide all child comments

How do you get from the value on the left to the value on the right?

| UUID | ? | |

It's not hex to base64 or hex to base58. That's when I gave up and decided to comradesource it.

Context

PeerTube creates two URLs for each video. The original, long one looks like this:

https://tankie.tube/videos/watch/2126816c-89f5-4aab-842f-65b9f3a39c8b

And the sleeker format looks like this:

https://tankie.tube/w/faLTidGsoG1G1TPLKUFcJh

The database only stores the UUID so the shorter ID must be a function of the first.

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[–] [email protected] 6 points 3 months ago (1 children)

It is int to base58. uuidToShort is the function, calling fromUUID from short-uuid.

There are multiple base58 implementations and I think this is the one bitcoin doesn't use, which might make an online base58 translator get it wrong. short-uuid calls it "flickrBase58."

This gets the correct answers:

def b58encode(fid):
  CHARS = '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ'
  CHAR_NUM = len(CHARS)
  encoded = ''
  fid = int(fid)

  while fid >= CHAR_NUM:
    div, mod = divmod(fid, CHAR_NUM)
    encoded = CHARS[mod] + encoded
    fid = div
  return CHARS[fid] + encoded

In [2]: b58encode(0x2126816c89f54aab842f65b9f3a39c8b)
Out[2]: '56qHyeZvHYZitUFukWo5rz'

In [3]: b58encode(0x8b9f9c446e1b485baf00c8b0e0067d59)
Out[3]: 'ieZJYUFB83oQacsNiQ55Bt'

In [4]: b58encode(0x72bd4bd2953843f381b2b8df991a32d8)
Out[4]: 'faLTidGsoG1G1TPLKUFcJh'

[–] [email protected] 4 points 3 months ago* (last edited 3 months ago)

Thank you!

party-blob gold-communist gold-antifa meow-bounce

It looks like the bitcoin implementation has the lowercase letters coming after the uppercase. That explains it. I assumed it was standardized.