Libelle (cipher)

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Libelle is a German cipher system, developed by the Federal Office for Information Security. The algorithm is not publicised, in an attempt to make cryptanalysis more difficult. Some experts think this security through obscurity is a bad approach, because public scrutiny of an algorithm would uncover potential weaknesses. In order to keep the algorithm secret, it is only distributed as a microchip named Pluto and not as a piece of software.

It is possible to have a secret cipher algorithm while still reaping the benefits of public cryptography research: one way is to make a non-weakening change to a public algorithm, like changing the Nothing up my sleeve numbers, or chaining the public cipher with an unrelated secret cipher. This is likely the case, as the unusual keylength of 168 bit heavily suggests 3DES as the core cipher.

[edit] See also

Skipjack

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