340,282,366,920,938,463,463,374,607,431,768,211,456 characters, pretty much for a bruteforce.
In 2007 there was estimation that cost to crack 88 bits using brute force is 300M$ if you apply Moore's law you reduce this price by factor 4 or you might get 2 extra bits by now.
So you need like 2^38 more money to crack just single 128bit key. (approx 10^20 $)
Source:
http://www.seagate.com/staticfiles/docs/pdf/whitepaper/tp596_128-bit_versus_256_bit.pdfSource 2:
http://dator8.info/pdf/AES/3.pdfFrom article abut 128 bit keys:
If you assume:
• Every person on the planet owns 10 computers.
• There are 7 billion people on the planet.
• Each of these computers can test 1 billion key combinations per second.
• On average, you can crack the key after testing 50 percent of the possibilities.
Then (see calculation reference in Appendix):
• The earth’s population can crack one encryption key (one drive only) in 77,000,000,000,000,000,000,000,000 years!
• In case you’re wondering, cracking the second key/drive would take another 77,000,000,000,000,000,000,000,000 years.
I just noticed, it is not calculated correct. Correct answer is 77e9 years (still bunch for our civilisation)
copied from stackoverflow
