Patent ID: 7404076

Claim:
An encryption communications system comprising: an encryption communications device; a plurality of terminals that are each operable to transmit to the encryption communications device an identifier, which is a bit string having a predetermined number of bits and is held by the respective terminal; and a management device that is operable to generate invalidation information showing one or more of the identifiers as information specifying one or more terminals to be invalidated, wherein the management device includes: an invalidation information generation unit operable to generate the invalidation information using a data format that generically expresses, by information specifying a value of a section in a bit string having the predetermined number of bits, all identifiers in which a value of the section matches the specified value; and an output unit operable to output the generated invalidation information, the encryption communications device includes: an invalidation information acquisition unit operable to acquire the invalidation information outputted by the management device; an identifier receiving unit operable, when an identifier is transmitted from one of the terminals, to receive the identifier; a judging unit operable to judge whether the received identifier matches any of the one or more identifiers shown by the invalidation information as information specifying one or more terminals to be invalidated; and a communication unit operable to (i) when judged to not be any matches, conduct a predetermined communication with the terminal that transmitted the identifier, and (ii) when judged to be a match, not conduct the predetermined communication with the terminal, the invalidation information (i) includes one or more sets of value and position information, each piece of value information showing a value of a section of a bit string having the predetermined number of bits, and a corresponding piece of position information specifying a bit position of the section in the bit string, and (ii) is information specifying, as a terminal to be invalidated, all terminals holding an identifier in which a value of a partial bit string located in a bit position specified by a piece of position information matches a value shown by a piece of value information corresponding to the piece of position information, and the judging unit (i) verifies, for each piece of position information, whether a value, in the received identifier, of a partial bit string located in a bit position specified by the piece of position information matches a value shown by a piece of value information corresponding to the piece of position information, and (ii) judges, when verified that there is at least one match, that the received identifier matches an identifier shown by the invalidation information.