A method for authenticating user data while preserving user privacy, comprising: - a) receiving, by a user device, from a verifier device, a request for getting the user data; - b) retrieving, by the user device, a predetermined first cryptogram and a predetermined decryption key; - c) sending, from the user device to the verifier device, the first cryptogram; - d) sending, from the verifier device to a server, the first cryptogram; - e) retrieving, by the server, based on the first cryptogram, a predetermined second cryptogram and a random that is pre-generated, the second cryptogram being generated using a predetermined encryption key and predetermined reference user authentication data concatenated with the random; - f) sending, from the server to the verifier device, the second cryptogram and the random; - g) storing, by the verifier device, at least temporarily, the random, as a reference random; - h) sending, from the verifier device to the user device, the second cryptogram; - i) decrypting, by or through the user device, the second cryptogram using the decryption key; - j) extracting, by or through the user device, the reference user authentication data and the random; - k) providing, by the user, the user device, with user authentication data; - l) verifying, by the user device, whether the provided user authentication data does or does not match the reference user authentication data; - m) providing, only if the provided user authentication data matches the reference user authentication data, by the user device, the verifier device or a verifier, with the random; - n) verifying, by the verifier device or the verifier, whether the provided random does or does not match the reference random; and - o) authenticating, only if the provided random matches the reference random, by the verifier device or the verifier, the user data, - wherein the user data includes at least one element of the following group: o at least one piece of information relating to the user; ∘ at least one biometric feature relating to the user; and ∘ at least one piece of information relating to a way of authenticating the user or user data. - a) receiving, by a user device, from a verifier device, a request for getting the user data; - b) retrieving, by the user device, a predetermined first cryptogram and a predetermined decryption key; - c) sending, from the user device to the verifier device, the first cryptogram; - d) sending, from the verifier device to a server, the first cryptogram; - e) retrieving, by the server, based on the first cryptogram, a predetermined second cryptogram and a random that is pre-generated, the second cryptogram being generated using a predetermined encryption key and predetermined reference user authentication data concatenated with the random; - f) sending, from the server to the verifier device, the second cryptogram and the random; - g) storing, by the verifier device, at least temporarily, the random, as a reference random; - h) sending, from the verifier device to the user device, the second cryptogram; - i) decrypting, by or through the user device, the second cryptogram using the decryption key; - j) extracting, by or through the user device, the reference user authentication data and the random; - k) providing, by the user, the user device, with user authentication data; - l) verifying, by the user device, whether the provided user authentication data does or does not match the reference user authentication data; - m) providing, only if the provided user authentication data matches the reference user authentication data, by the user device, the verifier device or a verifier, with the random; - n) verifying, by the verifier device or the verifier, whether the provided random does or does not match the reference random; and - o) authenticating, only if the provided random matches the reference random, by the verifier device or the verifier, the user data, - wherein the user data includes at least one element of the following group: o at least one piece of information relating to the user; ∘ at least one biometric feature relating to the user; and ∘ at least one piece of information relating to a way of authenticating the user or user data. o at least one piece of information relating to the user; ∘ at least one biometric feature relating to the user; and ∘ at least one piece of information relating to a way of authenticating the user or user data.