System and method for transferring the right to decode messages in a symmetric encoding scheme

(57) A summary and subject The framework of the encryption/decryption which supports the function which transfers the right of decoding of a message is offered. Solution means If the message m which needs to be transmitted to a grantor is given with a public key, the message m will choose a random number uniformly (910), and it will be enciphered by what (912) a pair of numbers (r, s) showing an enciphered message are calculated for. In order to commission a grantee the right of decoding, a grantor acquires the attestation decode key b of a grantee (914), and what (916) is calculated using it generates the substitute key pi. A message is changed into (r, s') from (r, s) by the calculation which used the substitute key pi (918). This message is decoded by a grantee from (r, s') after that by the calculation which used the attestation decode key b (920).