PURPOSE: To attain the ciphering with high secrecy by modifying the content of a text by an optional and temporary value as a time header at each node.

CONSTITUTION: At first a time header TH and then a data modified by the TH come. The header TH is 1 byte and takes values 00∼FF, and represents a time of each node and when a carry takes place, the value is counted up from the value 00 again. Further, the time at each node is counted up indepen dently and not necessarily synchronized. In decoding the text, the original data is generated by subtracting the each TH from the data of the text. When the result is negative in subtracting the TH from the data of the text, '1' is borrowed from the high-order and the result is to be positive.