Server apparatus, communication system, and data issuing method

A data verification system comprising:

• a plurality of devices connected in a wireless network;
• and
• a server apparatus, wherein
• the server apparatus includes:
• a data issuing unit to issue data to the devices in the wireless network, respectively;
• a data distribution manager to distribute the data issued by the data issuing unit to the devices, respectively;
• a data manager to manage a data set including the data issued by the data issuing unit;
• a revocation manager to detect, from the data set, data that satisfies a predetermined condition and invalidate the data detected;
• and
• a filter manager to:
• manage a revoked data set that is a set of pieces of data invalidated by the revocation manager;
• update a filter having a predetermined bit length each time the revocation manager invalidates data, by setting a first value to a bit onto which the revoked data set is projected when the revoked data set is projected onto the filter according to a definitive projection relation and setting a second value to a bit different from the projected bit in the filter;
• and distribute an updated filter to the devices in the network,
• the data manager:
• identifies, from the data set, reissuance target data other than the data invalidated by the revocation manager, the reissuance target data having projection onto at least one of bits whose bit value has changed from the second value to the first value between before and after the update of the filter, and having the first value for all of bits projected when the reissuance target data is projected onto the filter after the update;
• and for the device having the reissuance target data, reissues data having the second value for at least one of bits projected when that data is projected onto the filter after the update, by means of the data issuing unit, and distributes reissued data to the device, and
• the devices each include a network receiver to:
• test data presented by one device of the plurality of devices on a basis of the filter provided by the server apparatus;
• and determine that the data presented by the one device is invalid when all values of bits projected when the data is projected onto the filter are the first value.

A data issuing method comprising:

• issuing data to devices in a wireless network, respectively;
• distributing the data issued, to the devices, respectively;
• manage a data set including the data issued;
• detecting, from the data set, data that satisfies a predetermined condition and invalidate the data detected;
• managing a revoked data set that is a set of pieces of data invalidated;
• updating a filter having a predetermined bit length each time data is invalidated, by setting a first value to a bit projected when the revoked data set is projected onto the filter according to a definitive projection relation and setting a second value to a bit different from the projected bit in the filter;
• distributing the filter after update to the devices in the network,
• identifying, from the data set, reissuance target data other than the data invalidated, the reissuance target data having projection onto at least one of bits whose bit value has changed from the second value to the first value between before and after the update of the filter, and having the first value for all of bits projected when the reissuance target data is projected onto the filter after the update;
• and
• reissuing, for the device having the reissuance target data, data having the second value for at least one of bits projected when that data is projected onto the filter after the update and distributing a reissued data to the device.