Editing GNUnet (section)

=== Queries and replies ===
GNUnet Anonymity Protocol consists of queries and replies. Depending on load of the forwarding node, messages are forwarded to zero or more nodes.

Queries are used to search for content and request data blocks.

Query contains resource identifier, reply address, priority and TTL (Time-to-Live).

Resource identifier of datum <math>Q</math> is a triple-hash <math>H(H(H(Q)))</math>.{{sfn|GrothoffPatrascuBennettStef|2002|loc=5.5 More on queries}} Peer that replies to query provides <math>H(H(Q))</math>to prove that it indeed has the requested resource without providing <math>H(Q)</math> to intermediate nodes, so intermediate nodes can't decrypt <math>Q</math>.

Reply address is the major difference compared to [[Freenet]] protocol. While in Freenet reply always propagates back using the same path as the query, in GNUnet the path may be shorter. Peer receiving a query may drop it, ''forward'' it without rewriting reply address or ''indirect'' it by replacing reply address with its own address. By indirecting queries peer provides [[cover traffic]] for its own queries, while by forwarding them peer avoids being a link in reply propagation and preserves its bandwidth. This feature allows the user to trade anonymity for efficiency. User can specify an anonymity level for each publish, search and download operation. An anonymity level of ''zero'' can be used to select non-anonymous file-sharing. GNUnet's DHT infrastructure is only used if non-anonymous file-sharing is specified. The anonymity level determines how much cover traffic a peer must have to hide the user's own actions.

Priority specifies how much of its trust user wants to spend in case of a resource shortage.

TTL is used to prevent queries from staying in the network for too long.