Research On Theory And Application Of New-type Public Key Exchange Algorithms

The modern cryptography mainly consists of two parts: the symmetric encryption algorithms and the public key encryption algorithms(also called asymmetric encryption algorithms). The introduction of public key encryption marked as a revolution in the field of cryptography. Before the birth of public key encryption, cryptographers only relied on shared secret keys to achieve private communication. Public key techniques, in contrast, enable two parties to communicate privately without having agreed on any secret information in advance. The public key exchange algorithm is a crucial component in the public key algorithm settings. A public key exchange protocol allows two partners to communicate over an untrusted and unsecure channel to come up with a common secret value called a secret key, whereas an attacker should be unable to retrieve the key even with the ability to eavesdrop in the communication channel. The common secret key is subsequently used to provide privacy, authentication, data integrity, or for other cryptographic purposes. This thesis mainly focuses on researching new public key exchange algorithms. It includes the following three aspects.① The traditional public key exchange algorithms are mainly based on number theory. Neural synchronization by means of mutual learning provides an avenue to design public key exchange protocols, bringing about what is known as neural cryptography. Two identically structured neural networks learn from each other and reach full synchronization eventually. The full synchronization enables two networks to have the same weight, which can be used as a secret key. It is striking to observe that after the first decade of neural cryptography, the tree parity machine(TPM) network with hidden unit K =3 appears to be the sole network that is suitable for a neural protocol. No convincingly secure neural protocol is well designed by using other network structures despite considerable research efforts. With the goal of overcoming the limitations of a suitable network structure, in this thesis, a two-layer tree-connected feed-forward neural network(TTFNN) model for a neural protocol is developed and carefully studied.② Most of the existing public key exchange schemes are Diffie-Hellman(DH)-type, whose security is based on DH problems over different groups. Note that there exists Shor’s polynomial-time algorithm to solve these DH problems when a quantum computer is available, we are therefore motivated to seek for a non-DH type and quantum resistant key exchange protocol. To this end, we turn our attention to lattice-based cryptography. The higher methodology behind our roadmap is that in analogy to the link between ElGamal, DSA, and DH, one should expect a NTRU lattice-based key exchange primitive in related to NTRU-ENCRYPT and NTRU-SIGN. However, this excepted key exchange protocol is not presented yet and still missing. This missing key exchange protocol is found and carefully studied in this thesis.③ Mobile Ad Hoc networks(MANETs) are widely used in many areas. A group key agreement protocol allows a group of participants to communicate over untrusted, open networks to come up with a common secret value called a session key. Theoretically, group key establishment is more efficient than pairwise key establishment as the communicating nodes do not waste resources every time they wish to communicate with another device. It is provided in this thesis a spanning tree(ST)-based centralized group key agreement protocol for unbalanced mobile Ad Hoc networks(MANETs). Based on the centralized solution, a local spanning tree(LST)-based distributed protocol for general MANETs is subsequently presented. Both protocols follow the basic features of the HSK scheme. It is shown that the HSK scheme is a highly efficient uniform approach to handle the initial key establishment process as well as all kinds of dynamic events in group key agreement protocol for MANETs.