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Kerberos

Kerberos is an authentication protocol developed at MIT. It uses symmetric cryptography to provide a strong authentication for client/server applications across an otherwise open network.

Kerckhoffs´ Principle

An important principle in the evaluation of cryptographic algorithms. The security of the procedures should not be based on keeping the encryption function secret, but only the used private key.

Key Escrow

Key escrow means deposing the private key, i.e. the possibility for a superior authority to gain access to the private key of a user. This is not necessary if a private key is used for communication (data can be resend again), but for stored data there is a clear risk that key loss or damage could render critical data inaccessible

Key Exchange

The use of symmetric cipher algorithms requires that two communication partners decide on one joint key only known to them. The difficulty is that for the exchange of such information usually only partially secure channels exist. Additionally, protocols for key exchange must be prepared in such a way that only those pieces of information are exchanged which do not lead to knowledge of the real secret (the key). The most popular protocol of that type is Diffie-Hellman, whose presentation in 1976 can be regarded as the birth of public-key cryptography.

Key Management

To the key management belong all functions for the generation, distribution, storage, destruction and the updating of keys.

Knapsack Problem

The so called knapsack problem was one of the first problems used for public key procedures. The description is simple: You have a knapsack capable of carrying a certain weight, and a large number of entities of different masses. The problem is to select what to put in the knapsack to fill it optimally. For a large number of entities this is a really difficult problem, yet the algorithms based on it have all been proved to be insecure in the meantime.
Known Plaintext Attack. Expression for the situation in which an attacker knows the corresponding plaintext in an attack on the cipher. This is a serious problem since many messages are characterized by a certain format.

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