Method for controlling the identity of a user by means of a blockchain

An identity-controlling device to control the identity of a user, wherein the identity-controlling device comprises a communication interface with a public database of blockchain type and at least one processor configured to:

• give instruction for the reading in the public database of confidentiality-protected data, if any, previously generated by an identity-attesting device from an identity element of the user and at least one random datum specific to the user;
• verify heed of a condition relating to the found confidentiality-protected data;
• perform predetermined processing for the user only if the condition is heeded,
• wherein the confidentiality-protected data generated by the identity-attesting device are associated in the public database with first transaction data indicating that the identity-attesting device has transferred a predetermined amount of electronic currency to a recipient.

A client device intended to belong to a user, wherein the client device comprises:

• a communication interface with a public database of blockchain type;
• at least one processor configured to:
• generate proof data from an identity element of the user and at least one random datum specific to the user,
• give instruction for storing, in the public database, of the proof data so as to indicate that the proof data were generated by the client device, and in association with confidentiality-protected data previously generated by an identity-attesting device from one same identity element and one same random datum;
• perform the predetermined processing only if the found confidentiality-protected data and the proof data are related by a predetermined mathematical relation,
• wherein the confidentiality-protected data generated by the identity-attesting device are associated in the public database with first transaction data indicating that the identity-attesting device has transferred a predetermined amount of electronic currency to a recipient.