Deutschetelekom Ag

Ralf Schaffelhofer

Joerg Schwenk

Tobias Martin

Klaus Huber

Matthias Baumgart

Tim Schneider

Peter Windirsch

A method for establishing a common key for a group of at least three subscribers includes using a publicly known mathematical number group and a higher order element of the group g&#x2208;G. In the first step, a message corresponding to Ni: =gmod p is sent by each subscriber to all other subscribers (Tj), (zi) being a random number chosen from the set (1, . . . , p-2) by a random number generator. In the second step, each subscriber (Ti) selects a transmission key kij:=(g)for each other subscriber (Tj) from the received message (g), with i&#x2260;j, for transmitting their random number (zi) to the subscribers (Tj). In the third step, the common key k is calculated as k:=f(z, z, . . . , zn) for each subscriber Ti.

Method for establishing a common key for a group of at least three subscribers

A method for establishing a common key for a group of at least three subscribers includes using a publicly known mathematical number group and a higher order element of the group g&#x3b5;G. In the first step, a message corresponding to Ni:=gmod p is sent by each subscriber to all other subscribers (Tj), (zi) being a random number chosen from the set (1, . . . , p&#x2212;2) by a random number generator. In the second step, each subscriber (Ti) selects a transmission key kij:=(gfor each other subscriber (Tj) from the received message (g), with i&#x2260;j, for transmitting their random number (zi) to the subscribers (Tj). In the third step, the common key k is calculated as k:=f(z1, z2, . . . , zn) for each subscriber Ti.

In a method for compressing data, in which, in a data stream composed of characters, character strings are checked for correlation with other character strings that are present at a given distance in the data stream, and in which, in each case, the number of correlating characters and the position of the correlating characters within the respective other character string constitute the compressed data, at least one character is allowed to differ in the correlation check and data for correcting the at least one differing character is inserted into the compressed data.

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Darmstadt, Germany

Ralf Schaffelhofer