Reliable broadcast

This scheme is called a one-time signature scheme because each part of the secret key can be used only once, here for only one bit. (Later the term one-time will also be used for schemes where a complete message can be signed with each part of the secret key.) The most impractical feature of this scheme is the tremendous length of the public keys, because public keys have to be broadcast reliably at the beginning, whereas signatures need only be sent to one person and secret keys are simply stored. 

Artificial satellites, which are now used for communication, broadcast, weather forecast, etc., are equipped with a variety of semiconductor devices, which are often exposed to the high levels of radiation found in space. Such energetic particles, called cosmic rays, cause the degradation and malfunction of semiconductor devices, which lowers both the mission lifetime and reliability of satellites. Using ion beam irradiation facilities at TIARA, which have been uniquely adapted for simulating the radiation environment of space, we have... 

In the theoretical treatment of digital signature schemes, one simply assumes that a reliable broadcast network can be used during a special key-distribution phase. Only the real messages, later on, are sent over arbitrary channels. 

In particular, broadcast channels are assumed to be reliable even if some of the entities connected to them are corrupted. Thus, if a correct entity sends a message, all receivers receive exactly this message and know that it comes from this entity, and even if the sender is corrupted, it cannot trick the recipients into receiving different messages. One often speaks of the broadcast assumption if a broadcast channel is present in the structure of a system. 

There exists a distributed variant of authentication for this scheme (see Section 5.2.11), i.e., a protocol where either all the recipients accept a signature or none does [PfWa92b]. This is not trivial, even if reliable broadcast channels are given, because the entities of the recipients have different test keys. 

There is a two-party protocol for entities of one signer and one risk bearer with additional reliable broadcast channels where any number of entities of courts and recipients may listen, too. The interactive algorithm for the signer s entity is called A (for Alice, as usual) and that for the entity of the risk bearer B (because he is often the recipient. Bob). Both A and B may be — and will be — probabilistic. The random bit strings used by A and B are called and rg, respectively. 

External verifiability of authentication is easy to achieve because authentication is non-interactive, public keys exist, and test is deterministic and memory-less restr If the message exchange during authentication, i.e., sending the signature, takes place on a reliable broadcast channel (as it is standard when external verifiability is considered), all entities that took part in initialization can test the signature with the same public key. 

A correct execution of all the three algorithms, where P and V are connected with reliable broadcast channels that also lead to the input ports of Obs, and where the inputs par and K are the same for all three (see Figure 7.2), is denoted by a probabilistic assignment... 

Gen, the key-generation protocol, is a multi-party protocol defined by a pair of probabilistic interactive functions, (A, B ) (where is supposed to be executed by the signer s entity and by each entity of a tester), and arbitrary types of channels. (For concreteness, one can assume that in any execution, there is a private point-to-point channel between each pair of entities and a reliable broadcast channel for each one.)... 

Many military strategists believe that the greatest prospects for advancing a country s ability to fight more effectively lie in the development of more sophisticated tools for information warfare. Devices already available, such as GPS, surveillance satellites, and radar have proven effective in combat however, refinements to improve their accuracy and reliability, especially in the face of electronic countermeasures, will continue to be required. Electronic command and control tools—instruments such as the Internet and handheld devices that rely on satellites for broadcast capability—will also require constant updating or replacement with yet-undiscovered technologies that can give commanders improved ability to communicate with subordinates or superiors to direct activities and provide necessary support on the battlefield. 

A facility that is down for even 5 min can suffer a significant loss of productivity or data that may take hours or days to rebuild. A blackout affecting a transportation or medical center could be hfe threatening. Coupled with this threat is the possibihty of extended power-service loss due to severe storm conditions. Many broadcast and communications relay sites are located in remote, rural areas, or on mountaintops. Neither of these kinds of locations are weU known for their power reliability. It is not uncommon in mountainous areas for utihty company service to be out for days after a major storm. Few operators are willing to take such risks with their businesses. Most choose to install standby power systems at appropriate points in the equipment chain. 

The impact of satellites on world communications since commercial operations began in the mid-1960s is such that we now take for granted many services that were not available a few decades ago worldwide TV, reliable communications with ships and aircraft, wide-area data networks, communications to remote areas, direct TV broadcast to homes, position determination, and Earth observation (weather and mapping). New and proposed satellite services include global personal communications to hand-held portable telephones and broadband voice, video, and data to and from small user terminals at customer premises around the world. 

Motivated by the limitations of the MAC schemes proposed for VANETs, as discussed in Sect. 1.3, this brief introduces a multichannel TDMA MAC protocol which can provide a reliable one-hope broadcast service, necessary to support the QoS requirements of VANET periodic and event-driven safety applications. The rest of... 

H. A. Omar, W. Zhuang, andL. Li, VeMAC ATOM A-based MAC protocol for reliable broadcast in VANETs, IEEE Transactions on Mobile Computing, vol. 12, no. 9, pp. 1724—1736, Sept. 2013. 

Using the proposed scheme, a reliable broadcast service can be provided on the CCH. That is, if node x transmits a broadcast packet on time slot k, by listening to the L - 1 time slots following k, node x can determine the set Vx of one-hop neighbors which have not successfully received the packet, where T>x = y e Afx ID is not broadcast by node y. In other words, when node y includes ID in the header of its Typel packet, it is considered as an implicit acknowledgement by node y of receiving the packet broadcast by node x on time slot k. 

---