The math isn't too suspicious from what I can read, though I'm by no means an expert - it's just set stuff, from what I can tell. I think that Twitter post is j

The math isn't too suspicious from what I can read, though I'm by no means an expert - it's just set stuff, from what I can tell. I think that Twitter post is just confusing the different fonts for the sets vs the scalars. "The cardinality of the set of keys is equal to two to the power of the length of the key" is a pretty sensible statement. The Yi is probably a typo, considering the `Xi = Xi` on the prior line is a bit redundant (and this is preprint, so I'd forgive it). In any case, my real takeaway: > Our main result is that we can find a 64-bit key in about three days (average time) on two Odroid MC1 clusters (8 Gb) [18] from two pairs of plaintext/ciphertext. The algorithm isn't strong vs key reuse. I'm unsure if it actually claimed to be so - key reuse is almost always a big problem, though, and in this case they're exploiting the birthday paradox to make the search for the key more efficient.