Asymetric RSA Trapdoor Permutation

The RSA algorithm works the following

• Public Key: a large number n and exponent e
• Private Key: primes p and q such that n = p * q.

The RSA trapdoor permutation: x -> x^e mod n = y

So the strength in RSA is built around practical difficulty of factoring large integers.

Reference: https://en.wikipedia.org/wiki/RSA_Factoring_Challenge

See also https://www.theinquirer.net/inquirer/news/3019326/roca-rsa-encryption-key-flaw-puts-millions-of-devices-at-risk.