# Tag Info

1

Say $m$ is the number and $h=f(m)$ it will be pretty easy to find $m'$ (not necessarily equal to $m$) such that $f(m)=f(m')$ on a modern computer. Brute Force The output of $f(m)$ is 32 bits. The following python function will do it def find_collision(val): while True: test = random.getrandbits(32) target = ((test*test) >> 16) & 0xffffffff) ...

-3

I found that the best way to implement F is by using a T-function.

1

I don't think doing this by hand is the right way to do this. Pencil and paper systems are unreliable because humans just aren't as good at being robots as, well, robots! Most of the work in computing a secure MAC is hugely monotonous and a single mistake, anywhere during the process, could completely destroy any security you thought you had. If your ...

4

It is not entirely clear what you want, but suppose you need a trapdoor permutation - the function that is easy to invert only if you know a secret parameter - and which is not based on number-theoretic assumptions. There are two well known families of such schemes: Multivariate Cryptography (MQ) and Code-based cryptosystems (for instance, McEliece ...

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