AES - The Cipher That Is Almost Impossible to Break
AES - THE CIPHER THAT IS ALMOST IMPOSSIBLE TO BREAK
OK, so from the previous article, you know — or maybe you don't — that RSA has been theoretically broken;
In practice, the RSA key exchange protocol is hard to use and generally slow; NIST (the US National Institute of Standards and Technology) did not choose RSA as the standard cipher for national secrets but chose AES instead.
AES is almost impossible to break even with quantum computing. It is a symmetric cipher — that is, a single key is used for both encryption and decryption, so deploying AES is very simple without any convoluted key exchange protocol,
AES is a mixer: a piece of input information is thoroughly mixed using the key (cipher key) as the mixing formula. Normally, 1-1 mappings from symbol A to symbol B preserve the statistical properties of the original information, but AES not only maps symbols but also mixes with the key and with previous information, meaning A sometimes becomes B and sometimes becomes B', impossible to predict; the only way to decrypt is to know the key or brute-force it;
Brute-forcing AES is impossible, because the key is generally long; without loss of generality, AES256 uses a 256-bit key. Attacking this key generally requires the entire computing power of a Level-1 civilization on the Kardashev scale running continuously until the Sun burns all its fuel and goes dark — and it still would not finish. In other words, infeasible.
The key in AES has also been improved: part of the key becomes a Salt hidden by system developers as a secret-key, a component not easily found; combined with the user-defined key component, even if the user's key is "accidentally" leaked, the risk of immediate information exposure is reduced;
Because no quantum algorithm breaks AES yet, and it is unlikely one will be found — AES follows no specific rule, uses no elegant mathematics, it simply mixes everything up — quantum computing has no effect on breaking it; therefore AES is also considered a Post-Quantum algorithm;
[See more: The Cryptography Series]
Part 1: Breaking Enigma - Alan Turing
Part 2: Breaking RSA - Shor's Quantum Algorithm
Reference: AES, the cipher that (almost) cannot be broken, by PBS in the Infinite Series