Method for transferring the right to decode messages

A method for encrypting an original message to pass to a receiver by a transferor, the method comprising the steps of: obtaining a representative encrypted message the original message, which is encrypted (912, 1012, 1424) the encrypted message with a corresponding public key to the assignor according to a scheme of public key encryption; generation (916, 1016, 1428) of a key public delegation based on a private key that corresponds to the receiver and the private key corresponding to said public key of the assignor, wherein said private key of the assignor are combined and such recipient's private key; the combination of said private keys is based on subtraction of the private key of the transferor of the recipient's private key in the exponent of a modular exponentiation; and applying (918, 1018, 1430) of the public key delegation to transform the encrypted message into a transformed message, wherein the transformed message can be decrypted by the recipient using information selected from said private key corresponding to the receiver and the information available from the public key.