METHOD FOR THE INSERTION OF GUILLOCHE PATTERNS, METHOD FOR THE EXTRACTION OF GUILLOCHE PATTERNS, METHOD FOR THE AUTHENTICATION OF THESE GUILLOCHE PATTERNS AND DEVICES FOR IMPLEMENTATION

摘要

The invention concerns a method of inserting guilloche patterns in a document, each guilloche pattern being capable of encoding variable alphanumeric data ensuring a different aspect at each guilloche pattern so as to render said document secure, the method comprising an operation (300-600) of determining an insertion intensity of each guilloche pattern previously generated (100) on the basis of a mid-gray level of the document near said guilloche pattern. The invention also concerns a device for implementing this insertion method. The invention also concerns a method for extracting guilloche patterns (601 -608) from a secure document (600) likely to be degraded, the method comprising the following operations: - determining (710) a contrast card (c) of at least one portion of the secure document that includes the guilloche patterns; - identifying (720), on this contrast card an optimal percolation trajectory; and - extracting (730) the optimal percolation trajectory, said trajectory corresponding to the guilloche pattern. The invention also concerns a method of authentication of the guilloche patterns of a secure document likely to be degraded, involving: - the preceding extraction operations, and - an operation (740) of comparing each extracted guilloche pattern with a corresponding theoretical guilloche pattern.