Study of quantum cryptography protocols

The purpose of this thesis is to study quantum cryptography protocols and to evaluate their security. For this purpose, we will define suitable security models, construct or improve protocols and prove their security. From a practical perspective, we will contribute to the development of quantum protocols libraries by adding new functionalities and by optimizing the resources needed to implement them efficiently.

The protocols that interest us in particular are those we can regroup under the term “unclonable cryptography”, meaning the construction of cryptographic objects that cannot be copied. This is the direct consequence of one of the most fundamental results in quantum information - the so-called “no-cloning-theorem” - that ensures that a general quantum state cannot be copied. In a first time, we plan to study the functionalities linked to the concepts of “single decryption” and “copy protection”. Existing constructions only consider simple functions (called evasive functions). After we study them, our purpose will be to improve them and extend them to more complex functions.