Method and device for encrypting and decrypting digital data

1. A method for encrypting an initial digital data set, wherein it comprises a compression of the initial digital data set delivering a compressed set comprising at least one compressed digital data stream and at least one dictionary associated with the at least one compressed digital data stream, and an encryption of the at least one dictionary only, delivering an encrypted digital data set comprising said at least one compressed digital data stream and the at least one encrypted dictionary.

2. The encryption method according to claim 1 , in which the compressed set comprises a dictionary associated with several compressed digital data streams, or several dictionaries respectively associated with several compressed digital data streams.

3. The encryption method according to claim 1 , in which the initial digital data set is a paginated data set and the encrypted digital data set is stored, furthermore, in a paginated storage memory of an electronic system, for example a wireless communication apparatus.

4. A method for decrypting a digital data set encrypted by the encryption method according to claim 1 , on the basis of an initial digital data set, comprising a decryption of the at least one encrypted dictionary and a decompression of the at least one compressed digital data stream with the aid of the at least one decrypted dictionary so as to obtain the initial digital data set.

5. The decryption method according to claim 4 , comprising a storage of the encrypted digital data set in a paginated storage memory of an electronic system and a decryption of the dictionary during the booting of the electronic system.

6. The decryption method according to claim 5 , in which the electronic system comprises a virtual memory mechanism comprising a paginated work memory, the content of memory pages is transferred from the paginated storage memory to the paginated work memory and the encrypted digital data set contained in the memory pages is decompressed during the transfers of memory pages.

7. The decryption method according to claim 4 , implemented in a wireless communication apparatus.

8. A device for decrypting a digital data set encrypted on the basis of an initial digital data set, wherein the encrypted digital data set comprises at least one unencrypted compressed digital data stream and at least one encrypted dictionary associated with the at least one unencrypted compressed digital data stream and in that it comprises a decryption means able to decrypt the at least one dictionary and a decompression means able to decompress the at least one unencrypted compressed digital data stream with the aid of the at least one decrypted dictionary so as to obtain the initial digital data set.

9. The decryption device according to claim 8 , in which a paginated storage memory of an electronic system contains the encrypted digital data set and the decryption means is able to decrypt the dictionary during the booting of the electronic system.

10. The decryption device according to claim 9 , in which the electronic system comprises a virtual memory mechanism comprising a paginated work memory and a memory management unit which is able to transfer the content of memory pages from the paginated storage memory to the paginated work memory and in which the decompression means is able to decompress the encrypted digital data set contained in the memory pages during the transfers of the memory pages.

11. A wireless communication apparatus comprising a decryption device according to claim 8 .