this post was submitted on 31 Jan 2024
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I've done the math for how long it'd take to randomly guess the last several kilobytes until something checksummed correctly.
I was not pleased with the answer.
That would put those crypto miners to better use at least
You know I never thought of that.. but yeah that would be a good very very very very large number.
Like throwing puzzle pieces in the air and getting it to land completed.
On average it'll take 2^(n-1) guesses to reconstruct 2^n bits, so... depends on how many hashes / sec you can do.
Let me save you some time: not enough.
Haha agreed, if we're talking about kilobytes of missing data brute forcing is intractable.
There may be structure to exploit in the data format. E.g. if you're recovering missing content from a book written in English, you can probably get away with enumerating only printable ASCII and 90% of the letters will be lowercase.
But practically, I am unconvinced because the information density is pretty high on the kinds of things people like to torrent.
If its a piece at the beggining or end of the file it would likely be significantly easier
wait until you hear about collisions (missing more bits than your hash output length guarantees a collision on average)