New York Times Co. v. Estados Unidos

The coding of flow or coding by flood (in English stream cipher ) is one of the two main categories of modern codings in symmetrical Cryptographie, the other being the Chiffrement per block. A coding by flood manages to treat the data unspecified length and does not need to cut out them.

An not-exhaustive list of codings by flood:

• A5, used the mobile phones of the type GSM to quantify the communication by radio enters the mobile and the antenna-relay nearest,

• RC4, more spread, conceived by Ronald Rivest, used in particular by the protocol WEP of WiFi
• Py, a recent algorithm of Eli Biham
• E0 used by the protocol Bluetooth

A coding by flood often appears as a Générateur of pseudo-random numbers with which one operates a XOR between a bit on the outlet side of the generator and a bit coming from the data. However, the XOR is not the only possible operation. The operation of addition in a group is also possible (for example, addition between two Octet S, modulo 256). A coding per block can be converted into a coding by flood thanks to a Procedure which makes it possible to chain several blocks and to treat data of unspecified size.

Coding/deciphering with XOR

That is to say $\backslash \; oplus\; ~$ the Boolean operation XOR:

• Coding of the message M with the key K: $M\; \backslash \; oplus\; K\; =\; C~$

• Deciphering of the message C with the key K: $C\; \backslash \; oplus\; K\; =\; (M\; \backslash \; oplus\; K)\; \backslash \; oplus\; K\; =\; M\; \backslash \; oplus\; (K\; \backslash \; oplus\; K)\; =\; M~$

See too

• Cryptanalyse
• disposable Mask

Random links:

Oisy-the-orchard | Richard Oswald Karl Kräusel | Rodenstock | Gageo-C | Blunders, blunders and pellets | New_York_Times_Co._v._Etats-Unis

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