| 摘要 |
PURPOSE:To prevent the leakage of a secret by concealing an enable code by externally inputting a key code and then by obtaining the enable code by arithmetic with an ID code set in a decoder. CONSTITUTION:When a key code is inputted to the decoder, an enable code can be obtained by arithmetic with a characeteristic ID code set in the decoder. Multiplexer circuits IC1 and IC2 determine one of inputs by selecting an address. Key code K and the ID code are inputted to circuits IC1 and IC2, whose outputs are half-added by half-adding logic circuit G and enable code E is lead out of its output. In this case, the key code is so set that the obtained enable code E will be in common to all decoders. Thus, the enable code is concealed to prevent tapping and robbery. |
