The method for protecting a cryptography circuit from attacks aiming to discover a secret datum (Di, K) used during execution by the circuit of a cryptography algorithm comprising the application (22) of at least one cryptographic operation (Oi) to the data (Di), said data belonging to a first mathematical structure (E) having at least one group structure and provided with at least one binary operation, is characterized in that it comprises a step (OPi) for protecting said cryptographic operation, comprising applying (20) to said data (Di) at least one first reversible homomorphism (Mi), compatible with said binary operation, before applying (22) said cryptographic operation (Oi), and applying (24) at least one second hornornorphisrn (Mi−1), opposite the first homomorphism (Mi), after applying said cryptographic operation (Oi).