2 ms·
Neither is RSA. Most present day asymmetric crypto has its strength (amount of computing required to break it) significantly reduced by quantum computers. The s
by er4hn 6y ago
Neither is RSA. Most present day asymmetric crypto has its strength (amount of computing required to break it) significantly reduced by quantum computers. The solution is quantum safe algorithms which are a developing field.
Symmetric algorithms such as AES can have their strength reduced as well, but (I have no sources to cite) I believe this reduces it from 256-bit to 128-bit. At 128 bits of security it is still widely considered safe to use.
- jesboat 6y agoThe prototypical quantum attack for symmetric crypto is Grover's algorithm [https://en.wikipedia.org/wiki/Grover%27s_algorithm https://en.wikipedia.org/wiki/Grover%27s_algorithm] which finds "the unique input to a black box function that produces a particular output value". Whereas a classical computer would need to check an average of N/2 values (where N is the size of the domain), Grover's takes O(sqrt(N)). When you're measuring "bits of security", you say N=2^k, so a classical computer would take O(2^k) and Grover's would take O(sqrt(2^k)) = O(2^(k/2)), or a reduction from k bits of security from a classical adversary to k/2 bits of security from a quantum adversary. Hence the wisdom that AES-256 is approximately as secure post-quantum as AES-128 is to classical methods.
- er4hn 6y agofantastic explanation! Thanks so much for taking the time to write this up.