(computer security) Initialism of man-in-the-middleattack: Computer network crime where the criminal passes on messages between two communicating parties without them knowing it. The victims e.g. think they use a secure connection, but they don't know that this connection leads to the 'man in the middle' who relays the messages.
(cryptography) Initialism of meet-in-the-middle attack: Cryptographic attack that attempts to find a value in each of the ranges and domains of the composition of two functions such that the forward mapping of one through the first function is the same as the inverse image of the other through the second function
