Asymmetric cryptography and trapdoor one-way functions

The asymmetric-key (public-key) encryption scheme is considered to be the most important discovery in the history of cryptography. It is based on the use of two complementary keys generated according to a chosen trapdoor one-way function (TOWF). Since its first implementation, asymmetric encryption has revolutionized our way of communicating as well as the safety of information transfer, and it is now widely used around the world for various purposes, especially in the field of online transaction security. The safety of the asymmetric-key scheme relies on the assumption that any known cryptographic attack using an efficient problem-solving algorithm will not be able to succeed in applying the inverse (decryption) function onto the cryptogram in a polynomial time without additional knowledge (secret information). The most-challenging aspect of creating a new asymmetric cryptographic algorithm is selecting a one-way function for encryption purposes and finding a trapdoor in its inverse. In this paper, the concept of public-key cryptography will be explained using the RSA algorithm as an example. In addition, the review of the most-important functions that are considered to be trapdoor one-way functions will be conducted

One-time trapdoor one-way functions

Trapdoors are widely used in cryptography, in particular for digital signatures and public key encryption. In these classical applications, it is highly desirable that trapdoors remain secret even after their use. In this paper, we consider positive applications of trapdoors that do not remain secret when they are used. We introduce and formally define one-time trapdoor one-way functions (OTTOWF), a primitive similar in spirit to classical trapdoor one-way functions, with the additional property that its trapdoor always becomes public after use. We provide three constructions of OTTOWF. Two of them are based on factoring assumptions and the third one on generic one-way functions. We then consider potential applications of our primitive, and in particular the fair exchange problem. We provide two fair exchange protocols using OTTOWF, where the trapdoor is used to provide some advantage to one of the parties, whereas any (abusive) use of this trapdoor will make the advantage available to the other party as well.We compare our protocols with well-established solutions for fair exchange and describe some scenarios where they have advantageous characteristics. These results demonstrate the interest of one-time trapdoor one-way functions, and suggest looking for further applications of them