# What Is Trapdoor function?

## What Is Trapdoor function?

### Introduction

A trapdoor function is easy to compute function. It is informal to compute in one direction, however challenging to compute in the opposite direction deprived of special information, called the “trapdoor”. Trapdoor functions are usually used in cryptography.

### Description

In the terms of mathematics, if f is a trapdoor function, then there exists some secret information t, such that given f(x) and t, it is easy to compute x. Deliberate a padlock and its key. It is unimportant to amendment the padlock from open to close deprived of using the key. The key is being pushed into the bond into the lock mechanism. However, opening the padlock easily needs the key to be used. Here the key is the trapdoor and the padlock is the trapdoor function.

The product of two prime numbers “6895601” is an example of a simple mathematical trapdoor. What are those numbers?” A distinctive “brute-force” solution would be to try dividing 6895601 by several prime numbers until finding the answer. However, if one is told that 1931 is one of the numbers, one may find the answer by entering “6895601 ÷ 1931” into any calculator. This example is not a tough trapdoor function. Modern computers may predict all of the likely answers within a second. But this tester problem could be enhanced by using the product of two much larger primes.

Trapdoor functions arose to fame in cryptography in the mid-1970s. It came in cryptography with the publication of asymmetric or public-key encryption techniques by Diffie, Hellman, and Merkle. Definitely, Diffie & Hellman (1976) coined the term. Several function classes had been projected, and it rapidly became clear that trapdoor functions are harder to find than was primarily thought. Let’s say, an initial proposal was to use schemes based on the subset sum problem. Somewhat speedily, this turned to be inappropriate.

The RSA and Rabin families of functions are the best-known trapdoor function (family) contenders as of 2004. Together they are written as exponentiation modulo a composite number and equally are connected to the problem of prime factorization.

Functions linked to the hardness of the separate logarithm problem are not known to be trapdoor functions. They may whichever modulo a prime or in a group defined over an elliptic curve. Because there is no known “trapdoor” information about the group that allows the well-organized computation of discrete logarithms.

A trapdoor in cryptography has a very precise said meaning. It should not be confused with a backdoor. A backdoor is a thoughtful mechanism that is added to a cryptographic algorithm. For example a key pair generation algorithm, digital signing algorithm, etc., or operating system. That permits one or more unauthorized parties to bypass or undermine the security of the system in some fashion.