Quantum key distribution theory and practice

5.1 Network

We know that to share information between two entities, we need connexion and for that, there existe same models which were build by people and published after second world war by ARPA-NET project. That project was a PETENGONE project in second world war it was impossible for them to share or contact other bases for sharing data so the upcome of network idea. A network by definition is a group of two or more computers (Equipments) systems linked together..

A network follow a model and that model allows an implication of several steps which are called layers. Let us talk little bit about the composition of layer.

5.1.1 Model. In network, there exist two kinds of models that according to the convention of IEEE¹, The OSI and TCP/IP model. The OSI model is composed by seven layers and TCP/IP is composed with four layers. For our part QKD, we will be more interest in OSI model and try to explain how the QKD was implemented in the OSI model and how its works in this model also were precisely researchers implemented in classical model to become a quantum model. You can see in the figures how the models look like.

Figure 5.1: Network Model

5.1.2 Integration of QKD in the OSI model layers. In the begining of 21^st century, people used the genius idea to implement a QKD in the OSI model and this implementation was focus in some types of layers. The layers where QKD was implemented are session layer, network layer and the data link loyer. Those layers seem are more important.

The combination of QKD with other protocols in OSI model, is for an efficiency related to quantum field.

¹IEEE (Institute of Electrical and Electronics Engineers) is a organisation where all networks conventions are approved

Section 5.1. Network Page 26

Section 5.1. Network Page 27

We have a combination with a TLS/SSL in the session layer, in the network layer where more result are related to the connexion, the QKD find a cohabitation with an IPSEC protocol, the combination gives a new kind of protocol called SEQKEIP and the last layer, we have a Q3P is the mixage of QKD with PPP protocol.

Implementing a QKD in OSI model, give an explanation that the QKD network technology might be an essential part of modern security schemes for high performance distributed computing application. This implementation of secure scheme in OSI model was a project funded F6 called SECOQC which is a global network and the meaning is given by Secure Communication based on Quantum Cryptography. This project was developped by BBN technology, DARPA, researchers of Harvard University, Boston University in 2014. The combination give us the sophisticated protocol and QKD network architecture.

Figure 5.2: QKD implementation in OSI model

There exist a system which coordonate various network tools such that standard, open, general proposed protocols all those compose a system architecture and the system is called a grid. Grid computing is emerging as a modern technology to fulfill the high performance. Computing requirement of users, institutions and business organization world wide that was clear in [KX]

5.1.3 Functionality. In this point, we used a paper of [EAA]. The example take, is the integration of QKD in TLS/SSL for secure a transaction. That is related with online-commerce and palpaye classically, we have a secure server and protocol Htpps, the connection use TLS/SSL mode.

/This protocol ensure a integrity of the message and the encryption using point-to-point connection

between client and server. The combination of TLS/SSL with QKD is called QSSL and can be described as two principal modes. The first modes is about authentification of two sides which are communicating, that communication is in QKD.

The client and server after authentification, the following main operation continue to complete the generation of key size negociation and in the end of the operation of generating key size, the change-cipher-spec and finished messages can be exchanged.

The second method called the handshaking this method is a pre-shared keys initialization based on the previous model-1, the transactions (messages) are inserted before the transmission of change-cipher-spec and finished message.

The protocol QSSL has been added in the SSL record protocol. For this quantum cryptography with a principal toll QKD, can be integrated within SSL/TLS. In SSL, we have an additional parameter which is the Alert Protocol. Let us describe the fields than the messages follow in quantum cryptography and the fields can be represented in table where we will summarise

1. Describe the message use in public exchange phase of the QKD protocol with a type of 2 bytes

2. Specification of QKD protocol used type 1 bytes

3. Allows the use of more than one version of certain QKD protocol version 1 byte

4. length (4 bytes) the length of the messages is in bytes.

5. Jo. no 2 bytes QSSL session all operation multiple QKD protocol instance belong on it.

6. Authentification 1 bytes : specification of the message whether is authentificated. The idea of this point was taken in the article [EAA]

Type	Protocol	Version
	Length
Job no	Authentication	Encoding
	Content
	Tag

/The integration of QKD in network layers. The network layer is important because in this layer, when we want to ensure a point-to-point connection between two distinct people and to determine a data travel, the layer has a capacity to find the short way and quick one using some parameters for the reach the destinator. There are the most important job for this layer in OSI model and for the communication. The OSI model use what we call IPSEC² with a comming of QKD in 2003, BBN technologies found a way to integrate a QKD with the IPSEC protocol and that combination give the another current protocol named SEQKEIP³.

The new protocol which act with a main toll of quantum cryptography, has one idea in this construction and the idea is to stick, to traditional IPSEC and ISAKMP⁴. Those protocols, you can have some deep information like how its works in web site of RFC 2409, this is what we called norm RFC. QKD with

²Internet Protocol security

³Secure Quantum Key Exchange Internet Protocol

⁴Internet Security Association and Key Management Protocol

Section 5.1. Network Page 28

IPSEC gives a SEQKEIP, to build simply, we have to define two phases of Internet Key Exchange and that its the same as the use of ISAKMP mechanics, that takes an advantage to QKD in order to build a pratical protocol.

SEQKEIP have three mains in functionnality or phases: phase 1 is the negociation of the ISAKMP SA, phase 2 is negociation of SA and the last is phase 0, in this Alice and Bob will share the first secret key as adding in the phase. SEQKEIP have three modes, Quantum mode, Main mode, Quick mode. All those modes correspond to the phases listed in top. Quantum mode include quantum cryptography with a key exchange in phase 0, during the negociation phase of IASKMP SA, we can assimilate this phase to main mode and when we have the negociation of SA, the corresponding relation in SEQKEIP is the quick mode.

We can now explain how SEQKEIP works. We will see in the next figure, the action are numerated.

1. The fixation parameters of our protocol, that will be done with ISAKAMP SA and SA in other way is the combination of main mode and quick mode.

2. The implication of QKD using key Exchange with or either one-time-pad function

3. In last part, is the use of traductional symmetric cryptography algorithms for exchange of data.

We must put in mind that this operation, the lifetime of session key is so very short. Its equal to the time need to exchange the secret key using quantum cryptography. Whitout QKD, IPSEC work in the same manner. The idea of the quantum cryptography is to sift completely to the unconditional security function (QKD and OTP). You can find many explanation on [STH]

/Integration of QKD in data link : The data link provide the physical address service to the upper layer and is the only one add a queue to ensure the validation of data. This layer provide physical adress

Figure 5.3: SEQKEIP functionality

Section 5.1. Network Page 29

which is MAC address to the equipment. In classical part of network, the protocol used in this layer is PPP⁵ adding in this a quantum notion, we will leave a classical communication and will reach quantum networking. The combiation of PPP with QKD that provide a new protocol call Q3P.

The integratin of QKD in data link, provide some steps to achieve the right information. The steps that we list in this part we get inspiration in the writing of [EAA]. Let us illustrate brievely which steps for Q3P :

1. In this first step, we have an action of dead, establish, authentification. The three actions are identical to PPP, that mean the first phase pass through 3. The negociation of Encryption start just after the authentification operation for two nodes and the parameters are negociated also

2. The second phase is if the encryption key functions successfull, the requirement, the QKD phase will directly start. The encryption negociation is along the Key length and the TTL⁶ by sending a proper ECP⁷ packet

3. The quantum cryptography exchange will start directly with one goal to share a secret key in both nodes, that the goal of QKD. The encryption algorithm will be shared and the TTL of the key. The key that we get will be used in the network phase.

4. The data are sending through the channel, it is enciphered using the key production in the previous step and the algorithm also.

The following enumerate all the steps of Q3P. As we said that the TTL is short so far that when the

Figure 5.4: Q3P

TTL is expired, a new QKD phase start automatically. You can see in the picture how can we be build a network with the same equipment and include a QKD implementation in that network.

⁵PPP: Point-to-Point Protocol ⁶TTL: Time to life

⁷Ecryption Control Protocol

Section 5.2. Databases future work Page 30

Figure 5.5: Quantum network Architecture