A method for strong authentication of an individual by a server and a connected client device, the client device having a candidate biometric data of the individual and an image from an identity document representing at least one photograph of the individual and one optical reader data visible on the identity document. A cryptographic footprint includes extracting, by analysis of the acquired image and the optical reader data, calculating a first data decoded by application of a decoding process to the candidate information and to a first encoded data, such that the first decoded data matches first random data if the candidate information matches a reference information representative of the appearance of the photograph, verifying that a cryptographic footprint of a first concatenation of the extracted optical reader data and the decoded data coincides with the first cryptographic footprint, and a reference biometric data and the candidate biometric data match.