Re:Visualising how close random GUIDs come to being the same
by 8organicbits on Sunday August 17, 2025 @10:26AM
(#44931800)
That's great analysis. As you call out in the post, the 2^64 value is used to attack SHA256-128 (SHA256 truncated to 128 bits). NIST recommends at least SHA-224, which makes sense given your conclusions.
In any case, in 2023 I back-of-the-envelope estimated that you could compute 2^64 SHA256 for ~$100K, using rented GPU capacity https://www.da.vidbuchanan.co.uk/blog/colliding-secure-hashe...