Distributed OS: Winter 2011 Reputation Systems Paper

What is reputation?

In the real world, people are generally quite conscious of certain behavioural actions that make. These actions are expected to fall within the social norms and are scrutinized continuously by the people around us. On a daily basis, Individuals build a personal set of judgment values and opinions on others in the society. When we listen to a politician on the news, or interact with a friends, we are updating this image that we have of the individual or group. It is this image we generate that helps us make conclusions as to whether we like the individual, whether we trust the individual, or whether we can relate to the individual. The global opinions that others have on us is known as reputation.

A reputation system's main purpose is to facilitate in providing a means for assumptions to be made about the level of trust one can have for a particular person or situation in executing a task to our liking. It is important to note the importance of the word assumption. With the gathered information, we are able to generate an estimate of their actions. It is by no means accurate. Furthermore, reputation is not a globally accepted view of an entity. In some cases, an individuals reputation can be quite varied between different observers. Some may have encountered contact with the entity in a different context or had a different level of expectation compared to others. Likewise, some individuals might be falsely persuaded to confirm to specific opinions by large and powerful groups, whereas others have a crystallized and hard-to-change opinion.

How can reputation be used?

Reputation can be useful in acquiring an understanding of how congruent one's own goals are from another. If we are to accomplish a desired task that requires the cooperation of others, we carefully analyze whether the individuals we choose will be a good fit or whether they will hinder our progress. Or, worse yet, halt our progress completely.

In a more technical and distributed view, reputation is the process of recording, aggregating, and distributing information about an entity's behaviour in distributed applications. Reputation might be based on the entity's past ability to adhere to a mutual contract with another entity. As stated above, the validity of acquired reputation is largely subjective and unknown. Clearly, if we are to achieve an optimal reputation system we will need a fixed set of rules or norms that are expected to be followed in certain situations. If we look back to the analogy with human's, we are - to a fairly high degree - able to maintain order in some parts of the world by enforcing rules. It is unreasonable to think that we can prevent all wrong-doing. There are always outliers that will oppose the greater society, but eventually the greater community will overcome those outliers and prevent them from being detrimental to society. There is no perfect solution to maintaining social order in reality, and likewise, there is no perfect solution for maintaining good behaviour of computational entities.

The idea of enforcing rules or generating reputation of other entities to use in a decision-making process are both realistic options. This is known as the Emerge vs. Impose problem. Do we maintain records based on a fixed set of imposed rules? Or do we build rules as the system emerges and reputations are formed. In our opinion, we feel the answer is both.

What systems are currently in place?

Distributed systems such as the web, do not have a ideal reputation system in place.

Our assumptions

<Here we can talk about how we originally wanted to have a section on PKI, but changed our minds because it was veering too far from our core problem of reputation>

Generating reputation

How is reputation queried?

Querying reputation is the problem of how one entity in a reputation system acquires reputation data on another entity in the system that it does not already have. There will need to be an established way of requesting, receiving and finally analyzing the reputation data to decide if a connection should be made or not. This needs to be done because depending on the size of the system it's highly unlikely any given entity will know about another given entity if it has never communicated with it before. In a system like the internet it is unreasonable to expect the regular process of information dissemination to provide every entity information on every other entity. It is even more unreasonable to expect an entity in the system to be able to store all this information.

In the greater scheme of a reputation system, querying assumes some systems need to already exist. There needs to be a means of authenticating messages, as to limit the spread of false information and guarantee the integrity of the system. There needs to be a way of maintaining the history of the system, so that reputation events can be recorded and accessed. There needs to be a means of dissemination, as querying in this sense won't be suited for the gradual distribution of information. In short, for there to be querying of reputation, you need to have something worth querying.

But what does a system for querying need to address? It needs to be able to request information on demand, and receive that information quickly and efficiently. Specifically, the system needs to be able to handle any given entity in sending out a request for reputation information, and have other entities process that request and return a response. There needs to be a way for an entity to handle the likely event that there is no reputation information on another entity. Finally, the entity needs a way to process and interpret the information it receives.

As previously mentioned, in this paper, there are two primary layouts for a reputation system: hierarchical and distributed. Both of which will need to interact with each other. In a hierarchical-centralized system, there is a hierarchy of nodes who defer to each other. Any given node in the system will defer to an authority, known as its authority node. Most, if not all, reputation information will go through this node, and as far as their subordinate nodes are concerned, his 'views', or reputation data, will be absolute. In a distributed, peer to peer system, reputation information will be acquired from trusted peers.

--more coming

References

Why PKI should be ommitted reputation must be trusted = we get this trust through interactions. We BELEIVE this trust because we assume we have attribution!