Perhaps a better example of a one-way function vs. a trap door is with symmetric cryptography? Let's look at two examples of a 2^128 -> 2^128 function f(n):
- The first 128 bits of SHA2(n). It should be computationally infeasible to find n from the output.
- AES128(n, k). It should be computationally infeasible to find n from the output, unless you know k.
- The first 128 bits of SHA2(n). It should be computationally infeasible to find n from the output.
- AES128(n, k). It should be computationally infeasible to find n from the output, unless you know k.