ENCIPHERING/DECIPHERING METHOD AND ARRANGEMENT FOR PERFORMING THE METHOD

摘要

The invention relates to a method of enciphering information-containing digital data signals with the aid of enciphering keys and of deciphering a message thus enciphered, utilizing the same key. For usages in which high demands are made on the quality of enciphering the conventional method - the EX-OR adding together of clear text and key text on a bit basis - has shortcomings. The invention has for its object to provide a very reliable method with which furthermore the propagation of errors caused by any transmission errors is prevented. This is accomplished in that the (clear) text characters to be enciphered are processed using an enciphering key which is derived from a key text and that the nature of the processing operation performed on the clear text characters is determined by an instruction command which is also derived from the key text.