re how large are commercial keys in article apr ee eng ohio state edu butzerd maumee eng ohio state edu dane c butzer writes finally can anyone even concieve of a time place where bit keys aren t sufficient i certainly can t even at a trillion keys a second it would take about billion years to search just one billionth of that keys space it depends on the attack adding a bit to the key doubles the amount of work to be done in a straight brute force attack where you try every single possible key until one works processing and storage requirements for this kind of attack on a bit key seem like they ought to make it effectively impossible however there may be other attacks whose difficulty is for example proportional to say sqrt n or some such also a long key does you little good if there is a way to incrementally guess a little of the key at a time thanks dane john
