How Cryptographic Protocols help Design Healthy Society
Our daily life can be empowered with information technology if we can capture the essence of how an ideal function should be, and we can correctly implement it. Real world society takes advantages of physical properties and our activities are performed on top of these features. For example, we have paper envelopes that hide the message enclosed in the envelope. On the other side, cyber society built with information technology is free from limits of physical properties and enables fast transmission of data and fast duplication of data. While such property is favorable in efficiency aspects, it can be harmful for security and privacy aspects. Moreover, the IT systems can behave in a way that favors the designer or the administrator of the system, resulting unfair to the users or customers of the system. Cryptography is a tool that brings limitation in the cyber society. A data can be freely copied or sent out around, but only a person that have a legitimate key can recover information from the data. It is mathematically guaranteed that there is only negligible probability that someone can break the encryption. These powerful tools helps to design various functions in cyber society. In order to do so, we need to correctly model the target functionality, define its security, privacy and fairness requirements, and then design cryptographic protocols satisfying those properties. In the talk, we will discuss some examples such as electronic voting and electronic money (bit coin).