A large number of cryptographic authentication schemes and protocols have been designed to provide authenticated key agreements to prevent man-in-the-middle and related attacks. These methods generally mathematically link the agreed key to other agreed data, such as. B: The exponential key exchange does not give prior agreement or subsequent authentication between participants. It has therefore been described as an anonymous key memorandum of understanding. Although the Diffie-Hellman key agreement is itself a key, unauthtified protocol, it forms the basis of a multitude of authenticated protocols and is used to provide secrecy in volatile Transport Layer Security modes (called EDH or DHE depending on the encryption suite). If a third party listened to the exchange, they would know only the usual color (yellow) and the first mixed colors (orange-tan and light blue), but it would be difficult for that party to determine the final secret color (yellow-brown). To reintegrate the analogy with large numbers rather than colors in a real exchange, this provision is mathematically expensive. Even for modern supercomputers, it is impossible to calculate in practical time. Note: It should be difficult for Alice to solve Bob`s private keys or solve for Bob for Alice`s private key. If it`s not difficult for Alice to solve Bob`s private keys (or vice versa), Eve can simply replace her own pair of private/public keys, put Bob`s public keys in her private key, create a common secret key and solve Bob`s private key (and use this to solve the shared secret key).
Eve can try to choose a pair of public/private keys that allows her to easily solve Bob`s private key. If Alice and Bob share a password, they can use a key agreement (PK) authenticated by the password to prevent man-in-the-middle attacks. A simple scheme is to compare the hash of s concatenated with the independently calculated password at both ends of the channel. One of the features of these diagrams is that with each iteration, an attacker can only test one specific password with the other party, so the system with relatively weak passwords offers good security. This approach is described in ITU-T Recommendation X.1035, which is used by network standards G.hn.