System for the printing and reading of encrypted messages

摘要

A system for the metering of encrypted postage and similar indicia includes a device for printing such indicia and a device for reading such indicia. The printing is accomplished with a dot matrix printer driven by signals obtained by altering character generation signals with encryption signals. The interleaving is accomplished on a row-by-row basis by inserting delays from an encryption circuit into signals from a character generator circuit. The reading is accomplished by correlating received characters against a stored array of a symbols to determine the presence of a symbol, the extraction of coded data from character data of the received and identified character, and the comparison of the separated coded data with a reference code to determine the accuracy of the printed material. Thereby, forgery and alteration is inhibited. The coding is accomplished with the dot matrix format of the characters by displacing some of the dots slightly from the remainder so as to retain the general form of the character for recognition of the character while the displaced dots serve as the code for the encryption.