Password-authenticated Key Exchange


Password-authenticated Key Exchange (PAKE) is a special form of cryptographic Key-Exchange protocol was defined in Year 1992

Password-authenticated Key Exchange protocols distinguishing feature is the client will authenticate to the server using a password.

Password-authenticated Key Exchange provides that an eavesdropper or Man-In-The-Middle cannot obtain enough data to be able to Brute-Force or guess a password (or key) without further interactions with the parties for each (few) guesses. This property allow strong security can be obtained using weak passwords.

Password-authenticated Key Exchange is where two or more parties, based only on their knowledge of a password, establish a Cryptographic Key using an exchange of messages, such that an unauthorized party (one who controls the communication channel but does not possess the password) cannot participate in the method and is constrained as much as possible from brute force guessing the password. (The optimal case yields exactly one guess per run exchange.)

Password-authenticated Key Exchange has two basic classifications

Balanced Password-authenticated Key Exchange allows parties that use the same password to negotiate and authenticate a Shared Secret. This means that both parties have either password or, in some cases, Private Key for corresponding Public Key. In some scenarios PKI can be represented by Ephemeral Keys in order to simplify Key-Exchange and take less user interaction for Public Key management.

Augmented Password-authenticated Key Exchange is a variation applicable to Client-server scenarios, in which the server does not store password equivalent data. This means that an attacker that stole the server data still cannot masquerade as the client unless they first perform a Brute-Force search for the password. Either there is one more vector for application of AugPAKE. When it comes to Constrained Nodes Private Key absence could be huge deal and some of the most popular and secure Balanced PAKE methods simply could not be applied.


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