[Crittografia] Qualcuno può insegnarmi a crittoanalizzare Lep2 codice simmetrico

[P_1_6]

Lep2 symmetric cryptographic code


The key is a pair of numbers (a, b) such that (a ^ 2 + b ^ 2) / 2 = P where P is a prime number.


encoding


given an odd message n we create a number A = (n ^ 2 + m ^ 2) / 2 greater than P and m>n you cipher in this way (m*b+a*c+a*m-n*b, a*m+n*b-m*b+a*n) = (H, K)


decoding


m*b+a*n+a*m-n*b=H, a*m+n*b-m*b+a*n=K



Advantages:


You can not decipher:

for every message m there are infinite encrypted messages

each key potential generates a different message (No bruteforce)

if you have the message m and the encrypted message, you do not have the key





We recommend a and b 512-bit or higher

https://www.academia.edu/35935939/Lep2_ ... aphic_code

[Pappappero]

Non si capisce come avviene la decodifica.

Lavori modulo $P$? Modulo $A$?