Spying and malicious parties have two basic ways of monitoring traffic of a decentralized P2P network:

Traffic analysis is used to analyze content and addresses on a public network, and to determine that a particular protocol or form of communication is actually taking place.

Peer-to-peer SSL connections can help obscuring the content to outside parties (each node exchanges P2P headers and payloads with direct neighbors through SSL-encrypted channels).

Traffic analysis can go beyond analyzing the content. For example, it can find data belonging to an encrypted P2P protocol if it often sends data packets of the same size. Padding of data packets to a random size can prevent such kinds of analysis.

Eavesdropping means to determine who is talking to whom, and what data is exchanged. It consists of methods to subvert existing principles of anonymity.

Anonymity means that two parties can communicate while one or both cannot be identified by the other. Using the common internet transport protocols, this is impossible, however, peer-to-peer can make this possible.

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