Abstract: An authentication method between a client (2) and a server (4) sharing a secret (6) includes the following steps: the server (4) generates at least one random value (40); the server (4) computes a first encrypted value (46); the server (4) concatenates the random value (40) and the first encrypted value (46) to form a challenge (10); the client (2) extracts the random value (40) and the first encrypted value (46) from the challenge (10); the client (2) computes a second encrypted value (48); the client (2) compares the first (46) and second (48) encrypted values; and the server (4) is authenticated by the client (2) if the first (46) and second (48) encrypted values match.