This algorithm is arguably already patented: http://www.patentstorm.us/patents/5893120.html http://www.patentstorm.us/patents/5893120.html In fact, you may rem

This algorithm is arguably already patented: http://www.patentstorm.us/patents/5893120.html http://www.patentstorm.us/patents/5893120.html In fact, you may remember that Google was sued over this last year: http://news.cnet.com/8301-13577_3-20056192-36.html?part=rss&subj=news&tag=2547-1_3-0-20 http://news.cnet.com/8301-13577_3-20056192-36.html?part=rss&... Granted, using a timestamp to expire hash table entries is probably different enough from using a timestamp to evict cache entries where I would hope this wouldn't hold up in court, but IANAL and I could be totally wrong here. Another possibility is that there could be a totally different patent that already covers this algorithm.