There's a hilarious stackoverflow post about the work required to brute force aes128/256[0]. One of the answers quotes Applied Cryptography, which Schneier hims

There's a hilarious stackoverflow post about the work required to brute force aes128/256[0]. One of the answers quotes Applied Cryptography, which Schneier himself quotes here[1]. Summarizing the strength of AES-256, he writes: > [The amount of energy required has] nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space. [0] https://security.stackexchange.com/questions/82389/calculate-time-taken-to-break-aes-key https://security.stackexchange.com/questions/82389/calculate... [1] https://www.schneier.com/blog/archives/2009/09/the_doghouse_cr.html https://www.schneier.com/blog/archives/2009/09/the_doghouse_...