AES256 has 115, 792, 089, 237, 316, 195, 423, 570, 985, 008, 687, 907, 853, 269, 984, 665, 640, 564, 039, 457, 584, 007, 913, 129, 639, 936 possible keys (I&#x27;ve put spaces after the commas to allow HN to wrap because HN can have trouble with long strings lacking whitespace).<p>Suppose Amazon has some kind of super GPU that can try 1 trillion (10^12) keys per clock cycle, and rans at 1 THz (!0^12 Hz). Note that both of these far exceed any actual GPUs.<p>Suppose Amazon has a trillion of these available and you use them all. To search that entire key space would take 3669308250866118434801967410403995 years. On average you only have to search half the key space, which cuts this 1834654125433059217400983705201998 years.<p>Assuming that this computation can be done super efficiently...so efficiently that for each key tested only a single bit actually has to irreversibly change state, and that we are doing this in a system cooled by liquid helium, it would need a minimum amount of energy equal to the entire energy output of the Sun over 3.6x10^20 years. (I don&#x27;t remember if that is worst case or average, so let&#x27;s be generous and call it only 1.8x10^20 years worth of total solar energy output).