énveisfunksjon

An "énveisfunksjon" is a mathematical term that translates to "one-way function" in English. It describes a function that is easy to compute in one direction but computationally very difficult to invert. This means that given an input x, it is simple to calculate the output f(x). However, given the output y, it is extremely hard to find an input x such that f(x) = y.

The concept of one-way functions is fundamental in modern cryptography. While their existence is widely believed and assumed in many cryptographic protocols, a formal mathematical proof of their existence remains an open problem in computer science and mathematics. If a one-way function were proven not to exist, it would have profound implications for the security of many cryptographic systems.

Examples of functions that are widely believed to be one-way functions include cryptographic hash functions like SHA-256 and integer factorization. For instance, multiplying two large prime numbers together to get a product is easy. However, given only the product, finding the two original prime numbers is computationally very intensive for sufficiently large numbers. This asymmetry is what makes such functions useful for security applications like digital signatures and password storage. The difficulty of reversing the operation is the basis for security.