Patent ID: 7724896

Claim:
A method for transmitting messages between an emitter and at least one receiver, comprising: encrypting a message (m) to be transmitted by means of a key (a) associated to said emitter; sending the encrypted message to a conversion module including at least a conversion key (π a → b ) and a conversion function, said conversion module being placed between the emitter and said at least one receiver; converting the encrypted message received in the conversion module by at least one message encrypted in such a way as to be able to be decrypted by a key (b) specific to said at least one receiver, the conversion being carried out without the initial message appearing in plaintext in the conversion module, and resulting in as much messages in accordance to a number of receivers; sending the converted message to a certain receiver; and decrypting said converted message received by said certain receiver via the key b specific to said receiver; wherein the conversion key (π a → b ) of the conversion module depends on a non trivial value raised to a power of the key (a) bound to the emitter and of the key (b) bound to the at least one receiver.