A Key-Agreement Protocol

Client: UE A and UE B clients are registered under the different SIP proxy servers (A and . B, respectively). For the exchange of session keys between UE A and UE B, the operation was performed on the basis of the Diffe-Hellman key exchange protocol to ensure perfect confidentiality and prevent key attacks. Figure 7.1(b) illustrates the TW-KEAP method of exchanging keys between UE A and UE B. The data security protocol is the security protocol, such as SRTP, that is used to protect the media session. This protocol is vulnerable to a dictionary attack: a spy can simply record the first message (gx, h, IDA) and test the pw′ candidate passwords against h. If the opponent receives pw′ h=H(pw′,gx,IDA,IDB) for a value, it is very likely that he has found the password. Note that the password is never displayed directly in the log. Although the Diffie-Hellman (D-H) protocol is by no means the only useful key exchange protocol, it is used in a range of systems. D-H allows both parties to an exchange (Bob and Alice) to deliver part of the secret key.

This is done in such a way that the entire key is not sent over the unsecured channel. Thus, a snooper will not get the information needed to steal the secret key. The Minutes shall be as follows. We`ve already mentioned that resistance to offline dictionary attacks affects authentication. we now come back to this issue. As explained earlier, a PAKE protocol should not disclose a single piece of password information. This means that there can be no mechanism in place to ensure directly at both ends of the protocol that the correct password is being used by the other party. For example, the password cannot fill in an effectively verifiable equation, which happens to be the dummy protocol error in Fig. e49.5. In contrast, a digital signature scheme works in the same way, the main difference being that the long-term secrecy is cryptographically strong. This is the method behind STS.

Online dictionary attacks are active attacks in which the opponent tries to guess the password through successive login attempts: the opponent engages in the log again and again, tries different passwords, and when the opposing party stops canceling, the opponent knows that he has guessed the right password. It is clear that the design of the protocol cannot prevent this attack. However, a well-built PAKE should only allow you to test one password per login attempt. From that point on, it is up to the application that supports the protocol to specify how many unsuccessful attempts can be tolerated before, for example, the target account is locked. The purpose of a PAKE protocol is to perform an authenticated key exchange like those described above, but assuming that the long-term key hardware is just a password shared by both parties involved.3 Such a scheme combines the efficiency of key exchange in producing cryptographically strong session keys with the convenience of authenticating by knowing a simple password. demonstrated. Another security term specific to the password-based case is resistance to server compromise (see Refs. [6] or [7]). It occurs in the following case: if one of the two parties is a server that has a function of the user`s password and not the password itself. Any ordinary PAKE can easily be converted into a PAKE that is suitable for this situation, for example, by simply hashing the password.

(Common PAHs are sometimes called balanced protocols, while those resistant to server compromises are called extended PAHs.) This captures a realistic scenario: a server may contain features from many different users who log on with it to access different resources. Resistance to server compromise then essentially indicates that the server cannot impersonate a user unless it first performs a dictionary attack on the data it contains. Note that this notion is controversial, mainly because if the server data is actually compromised, it does not make sense to consider the associated passwords as secure, as they are trivially vulnerable to offline searches. Later in this chapter, we will focus on balanced PAHs. It is not easy to use passwords instead of long, cryptographically strong keys to authenticate key exchange protocol flows. For example, a password cannot simply replace a strong symmetric key as input for a traditional key exchange protocol. There are two main reasons for this. AuthIP performs mutual authentication between two peers. An SA is configured that allows you to further configure SAs for ESP and AH traffic.

This is a request/response protocol, which means that the initiator peer sends a message to the responding peer. The responding peer then sends a message back to the initiator peer. AuthIP is typically used to negotiate esp transport mode traffic between two peers, but you can also use it to protect AH traffic. An example of a key transport protocol is one where a player generates a symmetric key and encrypts the key under the recipient`s public key using asymmetric cryptography. This is a key transport protocol (sometimes called a key encapsulation mechanism or KEM) and not a key agreement because the key depends on the input of only one party: the sender. The key is generated by one party and then transported to the other party. In an effort to avoid the use of additional out-of-band authentication factors, Davies and Price proposed using Ron Rivest and Adi Shamir`s locking protocol, which underwent both attacks and subsequent improvements. Figure e49.5.

Dummy password authentication protocol. The SAs for each session, including encryption and authentication method, IKE protocol, VPN type, peer and local IP addresses and gateway ID, security settings index, and Phase 1 authentication method. If you have a secure way to verify a shared key on a public channel, you can perform a Diffie-Hellman key exchange to derive a shared key in the short term and then authenticate that the keys match. One option is to use a reading authenticated by the key language, as in PGPfone. However, voice authentication presupposes that it is not possible for a man in the middle to falsify one participant`s voice in real time for the other, which can be an undesirable hypothesis. Such protocols can be designed to work even with a small public value, e.B a password. Variants of this theme have been suggested for Bluetooth pairing protocols. MIKEY can be integrated into session build minutes.

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