1. A method of registration and recognition of a user of a service, through identification codes derivable from biometric data, comprising the steps of: a. registering a user, through a respective registration event, wherein each registration event comprises: acquiring from the user to be registered at least one biometric datum of the user; encoding, by a coding procedure, the at least one acquired biometric datum into a respective registration identification code of the user to be registered; associating said registration identification code to the user to be registered; registering the user as a registered user, and the associated registration identification code as the registration identification code of the registered user; b. recognizing a registered user, among a plurality of registered users, through a respective recognition event, comprising: acquiring from the user to be recognized said at least one biometric datum of the user; encoding, by said coding procedure, the at least one acquired biometric datum into a respective recognition identification code of the user to be recognized; preparing, based on the registration identification codes, registered at a plurality of registration events, a comparison set comprising a plurality of comparison identification codes; comparing the recognition identification code with each of said plurality of comparison identification codes; estimating, for each of said comparisons, a respective matching level; recognizing or refusing recognition of the user to be recognized based on the estimated matching levels; wherein said steps of acquiring comprise acquiring a digital image of a hand of the user by a digital acquisition device; wherein each of said comparisons between the recognition identification code and one of the comparison identification codes comprises processing carried out by applying at least one trained algorithm, and wherein the recognition event further comprises the step of further training said at least one trained algorithm.