Elliptic Curve, Diffie Hellman, Discrete Log, Elgamal Encryption.
well-defined approach to find x for any number. 2^x (mod 19) So, formally the problem states: find x where g^x is congruent to h mod p where p is a prime and h is a number not divisible by p. Now, this problem isn’t known to have a polynomial time solutions and proves to be a very powerful trapdoor