Possible number of key combinations with respect to key size:
Time to crack Cryptographic Key versus Key size
As shown above, even with a supercomputer, it would take 1 billion billion years to crack the 128-bit AES key using brute force attack. This is more than the age of the universe (13.75 billion years). If one were to assume that a computing system existed that could recover a DES key in a second, it would still take that same machine approximately 149 trillion years to crack a 128-bit AES key.
There are more interesting examples. The following snippet is a snapshot of one the technical papers from Seagate titled “128-bit versus 256-bit AES encryption” to explain why 128-bit AES is sufficient to meet future needs.
- 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% of the possibilities.
Then the earth’s population can crack one encryption key in 77,000,000,000,000,000,000,000,000 years!
The bottom line is that if AES could be compromised, the world would come to a standstill. The difference between cracking the AES-128 algorithm and AES-256 algorithm is considered minimal. Whatever breakthrough might crack 128-bit will probably also crack 256-bit.