Method and device for encrypting a digital data stream in a transmission system
OwnerFrancesc Dalmases, Joachim Kahlertinventors
Life of this patent
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Abstract
A method for encrypting a digital data stream (d(k)) by means of a dynamic orthogonal spreading code (g1(k), g2(k)gH(k)) and through the assignment of a hop interval (Ihop), which varies from one connection to another. The degree of encryption is furthermore increased by varying the sequence of use of the content of a set (Gi) of spreading codes, which is defined by stating the positions ({p—1, p—2 . . . p-MI) in a permutation function (Si).
Claims9
A method for encrypting a digital data stream in a transmission system that uses orthogonal codes for the modulation, wherein—a kth transmitter constructs a kth connection for the kth digital data stream (d(k)),—for the encryption, the digital data stream (d(k)) of the transmitter is mixed with a spreading code that is assigned to this kth connection,—different spreading codes (g1(k), g2(k) . . . gH(k)) from a defined set (Gi) are assigned and—through the mixing a transmission signal (S(k)) is produced, characterized in that the degree of encryption of the kth digital data stream (d(k)) is increased during the kth connection through the allocation of ● a sequence for the application of the different spreading codes (g1(k), g2(k) . . . gH(k)) and/or a hop interval (Ihop).
A method for encrypting a digital data stream that is to be transmitted, wherein after the connection set-up, necessary parameters for the transmission and recovery are transmitted, characterized by the steps:
- communication of an encryption key (200) and thus:
- establishment (210) of a permutation function (Si),
- establishment (220) of a set (Gi) of spreading codes, and/or
- establishment (230) of a hop interval (Ihop),
- wherein the last three steps mentioned (210, 220, 230) can be carried out in any order.
A method for encrypting a digital data stream, characterized by the execution of a first permutation procedure (400) which contains a loop with the following steps:
- setting (410) of an interval (n) to “1”;
- waiting (420) for the end of a predefined hop interval (Ihop);
- increasing (430) the interval (n) by the value 1;
- carrying out a comparison (440) to see whether the current value of the interval (n) is greater than the total number (M) of the elements of a permutation function (Si) which states the positions of the spreading code (gn) of a set (Gi) of spreading codes that is to be used for encrypting the digital data stream, wherein alternatively the following takes place:
- if the comparison has a positive result:
- resetting of the interval (n) to “1”;.
- if the comparison has a negative result:
- equating the current spreading code (gn) with the spreading code (gp—n) that stands at the position (p_n) stipulated by the permutation function (Si) .
A method for decoding a received digital data stream that was sent encrypted, characterized by the execution of a second permutation procedure (800) that contains a loop with the following steps:
- setting (810) an interval (n) to “1”;
- waiting (820) for the end of a predefined hop interval (Ihop);
- increasing (830) the interval (n) by the value 1;
- carrying out a comparison (840) to see whether the current value of the interval (n) is greater than the total number (M) of the elements of a permutation function (Si) which states the positions of the spreading code (gn) of a set (Gi) of spreading codes that is to be used for decoding the encrypted digital data stream, wherein alternatively the following takes place:
- if the comparison has a positive result:
- resetting of the interval (n) to “1”;
- if the comparison has a negative result:
- equating the current spreading code (gn) with the spreading code (gp—n) that stands at the position (p_n) stipulated by the permutation function (Si)
Use of one of the methods mentioned above in a cordless or line-based network.
Dependencies are inferred from the claim text.