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Quantum key distribution protocol (QKDP's) which safeguards security on large network by using key agreement. The sender and the receiver register themselves into the separate database maintained for them and then a security key is generated whenever each user either on the sender or the receiver side makes login. In network each user uses these secret key .Each user has unique Secrete and which will be shared by each user to Trusted Center. In Trusted Center a Key is generated for network Security by using Algorithms and Quantum Mechanics.
Quantum Key Distribution (QKD) is a method of securely distributing cryptographic key material for subsequent cryptographic use. Actually it is sharing of random classical bit strings using quantum states. This uses a set of non-orthogonal quantum states then requires this key material to be considered quantum information. During transmission of key bits quantum encoding of cryptographic keys are valuable because the no-cloning theorem and the superposition principle governing quantum states confer a distribution is uniquely powerful form of information security. Once a random key is securely shared it cannot be breakable since it is the cryptographic method. For acquiring maximal security, it can be followed by one-time pad message encryption.
Quantum key distribution-the creation of secret keys from quantum mechanical correlations-is an example of how physical methods can be used to solve problems in classical information theory. A secure communication is obtained by using Quantum Cryptography, or Quantum Key Distribution (QKD), which uses quantum mechanics. It enables two parties to produce a shared random bit string known only to them, which can be used as a key to encrypt and decrypt messages.
Quantum cryptography is used to detect the presence of any third party who is trying to gain the knowledge of key when two user communicating. The process of measuring a quantum system in general disturbs the system is result from the fundamentals of quantum mechanism. The detectable anomalies are used to find the third parties who are trying to eavesdrop. By using quantum superposition or quantum entanglement and transmitting information in quantum states, a communication system can be implemented which detects eavesdropping. If the level of eavesdropping is below a certain threshold a key can be produced which is guaranteed as secure (i.e. the eavesdropper has no information about), otherwise no secure key is possible and communication is aborted.
The security of quantum cryptography relies on the foundations of quantum mechanics, in contrast to traditional public key cryptography which relies on the computational difficulty of certain mathematical functions, and cannot provide any indication of eavesdropping or guarantee of key security.
Quantum cryptography is only used to produce and distribute a key, not to transmit any message data. This key can then be used with any chosen encryption algorithm to encrypt (and decrypt) a message, which can then be transmitted over a standard communication channel. The algorithm most commonly associated with QKD is the one-time pad, as it is provably unbreakable when used with a secret, random key.
Three-party key distribution protocol
Three-party key distribution protocol allows two user in the distributed system to obtain the same session key from a trusted server via the shared private key between each party and trusted server.These protocols are basic building blocks for contemporary distributed system (eg. three-party key distribution protocol can be used as a modular for constructing three-party key exchange protocol ).
Session key distribution in the three-party setting is studied by Needham and Schroeder, which is the trust model assumed by the popular Kerberos authentication system . The provable security for three-party key distribution is provided by Mihir Bellare and Phillip Rogaway by giving the definition of security called AKE-security . (It is emphasized that AKE-security is also an accepted definition of security of other cryptographic tasks, such as group key exchange and key exchange.)
R.Canetti [5, 6] proposed a general framework for representing cryptographic protocols and analyzing their security. The framework allows defining the security properties of practically cryptographic tasks. Most importantly, it is shown that protocols proven secure in this framework maintain their security under a very general composition operation, called universal composition, with an unbounded number of copies of arbitrary protocols running concurrently. Similarly, definitions of security formulated in this framework are called universally composable (UC).
The definition of AKE-security follows a definitional approach which is called "security by indistinguishability". In contrast, definitions in the UC framework follow a different definitional approach which is referred to as "security by emulation of an ideal process". In the last few years, researches on the relation between indistinguishability-based definition of security and emulation-based definition of security have become one of the significant topics in cryptography .
One case where definitions follow the two approaches were shown to be equivalent is semantically secure encryption against chosen plaintext attacks. However, in most other cases the two approaches result in distinct definitions of security, where the emulation approach usually results in a strictly more restrictive definition. One example, there exists an AKE-secure group key exchange protocol is not UC-secure . Another example, a key exchange protocol is AKE-secure but do not satisfy the emulation-based definition of security .
The definition of UC security for three-party key distribution protocol is strictly more stringent than AKE-security. So a real-life protocol which securely realizes the formulated ideal functionality with respect to non-adaptive adversaries is proposed. Therefore, the formulated functionality with security-preserving composition property can be used as a simple building block for modular designs and analysis of complex cryptographic protocols.
The combination of 3AQKDP (implicit) and 3AQKDPMA (explicit) quantum cryptography is used to provide authenticated secure communication between sender and receiver.
In quantum cryptography, quantum key distribution protocols (QKPS) employ quantum mechanisms to distribute session keys and public discussions to check for eavesdroppers and verify the correctness of a session key. However, public discussions require additional communication rounds between a sender and receiver. The advantage of quantum cryptography easily resists replay and passive attacks.
A 3AQKDP with implicit user authentication, which ensures that confidentiality, is only possible for legitimate users and mutual authentication is achieved only after secure communication using the session key start.
In implicit quantum key distribution protocol (3AQKDP) have two phases such as setup phase and distribution phase to provide three party authentications with secure session key distribution.Â In this system there is no mutual understanding between sender and receiver. Both sender and receiver should communicate over trusted center.
In explicit quantum key distribution protocol (3AQKDPMA) have two phases such as setup phase and distribution phase to provide three party authentications with secure session key distribution.Â There is a mutual understanding between sender and receiver. Both sender and receiver should communicate directly with authentication of trusted center.
Disadvantage of separate process 3AQKDP and 3AQKDPMA were providing the authentication only for message, to identify the security threads in the message. Not identify the security threads in the session key.
In quantum cryptography, quantum key distributionÂ protocols (QKDPS) employ quantum mechanisms to distribute session keys and public discussions to check for eavesdroppers and verify the correctness of a session key. However, public discussions require additional communication rounds between a sender and receiver and cost precious qubits. By contrast, classical cryptography provides convenient techniques that enable efficient key verification and user authentication.
Man-in-the-middle attack is the form of attack on cryptography. Often abbreviated MITM, bucket-brigade attack, or sometimes Janus attack, is a form of active eavesdropping in which the attacker makes independent connections with the victims and relays messages between them, making them believe that they are talking directly to each other over a private connection, when in fact the entire conversation is controlled by the attacker. The attacker must be able to intercept all messages going between the two victims and inject new ones, which is straightforward in many circumstances (for example, an attacker within reception range of an unencrypted Wi-Fi wireless access point, can insert himself as a man-in-the-middle).
A man-in-the-middle attack can succeed only when the attacker can impersonate each endpoint to the satisfaction of the other - it is an attack on mutual authentication. Most cryptographic protocols include some form of endpoint authentication specifically to prevent MITM attacks. For example, SSL authenticates the server using a mutually trusted certification authority.
The man-in-the middle attack intercepts a communication between two systems. For example, in an http transaction the target is the TCP connection between client and server. Using different techniques, the attacker splits the original TCP connection into 2 new connections, one between the client and the attacker and the other between the attacker and the server, as shown in figure 1. Once the TCP connection is intercepted, the attacker acts as a proxy, being able to read, insert and modify the data in the intercepted communication.
Figure 1. Illustration of man-in-the-middle attack (Ref: http://www.owasp.org/index.php/File:Main_the_middle.JPG)
The MITM attack is very effective because of the nature of the http protocol and data transfer which are all ASCII based. In this way, it's possible to view and interview within the http protocol and also in the data transferred.
The MITM attack could also be done over an https connection by using the same technique; the only difference consists in the establishment of two independent SSL sessions, one over each TCP connection. The browser sets a SSL connection with the attacker, and the attacker establishes another SSL connection with the web server. In general the browser warns the user that the digital certificate used is not valid, but the user may ignore the warning because he doesn't understand the threat. In some specific contexts it's possible that the warning doesn't appear, as for example, when the Server certificate is compromised by the attacker or when the attacker certificate is signed by a trusted CA and the CN is the same of the original web site.
MITM is not only an attack technique, but is also usually used during the development step of a web application or is still used for Web Vulnerability assessments.
Eavesdropping is the process of gathering information from a network by snooping on transmitted data.
By this attack the information remains intact, but its privacy is compromised.
It can take place over wired networks as over wireless networks. On wired network the operation of eavesdropping is more difficult because it needs the eavesdropper to tap the network, using a network tap which is a hardware device that provides a way to access the data flowing across the network. And that of course can't be achieved unless the eavesdropper can be in touch with the wire of the network which is difficult sometimes and impossible the other times.
Eavesdropping can also take place on wireless networks where the eavesdropper is not obliged to be in the dangerous position of being compromised. All what he needs is a computer supplied by a wireless network adapter working on promiscuous mode to allow a network device to intercept and read each network packet that arrives even with other network address, to be in the area of the wireless network coverage and to have one of the particular software tools that allows the eavesdropping over Wi-Fi. Wi-Fi-short for "wireless fidelity"-is the commercial name for the 802.11 products. 
An example of eavesdropping is intercepting credit card numbers, using devices that interrupt wireless broadcast communications or tapping wire communications which is the preferable for eavesdroppers.
Eavesdropping can be useful by capturing none encrypted data or known decrypted, encrypted data, but it will be none useful if the data was encrypted by unknown encryption.
A replay attack is a form of network attack in which a valid data transmission is maliciously or fraudulently repeated or delayed. This type of attack occurs when a third party captures a command in transmission and replays it at a later time. By capturing the correct messages, an intruder may be able to gain access to a secure computer or execute commands which are normally encrypted and unreadable. It is often not necessary to decifer the command to use it .Replay attacks are typically simple to perform and require little or no sophistication. 
This type of attack is carried by originator or by adversary. In the replay attack, an attacker intercepts the data and retransmits it. It is a masquerade attack by IP packet substitution (such as stream cipher attack).
The Replay attack is simple because it is not difficult to capture the commands to be replayed. A user on a network can run a sniffer program and capture all packets that travel over the network.
This attack does not rely on traffic analysis and can confirm the communication relationship on Tor quickly and accurately, posing a serious threat against Tor. In the replay attack, an attacker may control multiple onion routers, similar to other exiting attacks , .