Forum Thread: Cracking a 64-Bit Encryption

64-bits is equivalent to 8 bytes. How many possible combinations are in 8 bytes? That's 2^64 = 1.8x10^19 (19 zeroes) possible combinations to brute force. How many combinations can your computer do in one second? Let's say 10 million a second for a fast PC. That's 1.8x10^12 seconds or, 512409558 hours or, 21350398 days or, 58654 years. Definitely not an option for you.

Source: Lock Down

How on earth could you calculate this!! what you described is but an approximation of a brut force on a symmetric encryption!! first of all the encryption scheme will greatly impact the set of possible combinations. So using a 64 bit key doesn't imply that their are 2^64 combinations, we call them effective bits. This is what allowed the DES 64bit to be brute forced in 1998 (EFF DES cracker). Also where did you get the 10 million operation, and decrypting a cipher is not one operation but a set of operations. it is preferable to talk in flops. But then again the encryption scheme is the most important factors, It is not difficult to prove that a 128 bit symmetric encryption can rival in "strength" 2048 bit asymetric key.

what are you trying to get into such as do u know the person and other such things if you do add that to a dictionary crack and run that along with an algorithm to try to guess it by looking at the non plain text (sorry i forgot the word) and try it like that.

If you want to crack a key, the first thing you need to do is to know what algorithm was used for the encryption. a 64 bit assymetric RSA can be brut forces in a matter of hours with a home PC. Using GPUs could bring down the necessary time to seconds. i would invite you to read the 25 GPU devour passwords in seconds an article from 2012 that shows how any XP password would take less than 6minutes to be cracked. On the other hand with elyptic curve cryptography, even a quantum computer would have troubles breaking it. This is why the algorithm is important.

I can crack it in around 1 sec using GPU