[1]https://blockexplorer.com/q/hashestowin
   log(171833398380382098659*24*60*7)/log(2)
   Gives context to the obsolescence of 80-bit block ciphers (it only
   takes ten million dollars of dedicated hardware to crack an 80-bit
   cipher). And context to the NSA's design of Skipjack.
   Naturally even a 2^64 collision attack requires implausible amounts of
   storage, so properly designed hash functions should be secure for the
   indefinite future.

References

   1. https://blockexplorer.com/q/hashestowin