Irreversible encryption method by generation of polynomials.

Patient follow up, within the framework of epidemiological studies, poses the problem of linking nominal files. An encryption method of identity is proposed to allow the linkage of medical information on the same patient while respecting the confidentiality of medical data. In contrast with most encryption algorithms, the proposed method is mathematically irreversible in response to the requirement of the French National Commission of Computerized Information Security which demands that the cryptosystem must not be decipherable even by the legitimate recipient. In order to prevent deciphering by frequency analysis, the proposed method introduces polynomial operations so that neither indication concerning the length of the string nor a possible repetition of characters can be obtained by code disclosure. The security of the system is reinforced by the use of two keys, the first one to be defined by the producers of information and the second one by the recipient so that nobody can decrypt the enciphered text.