Editing (Symmetric) Private Information Retrieval (section)

====Multi-database protocols====
It is possible to achieve information-theoretic (S)PIR with reduced communication complexity (i.e., compared to this of the trivial solution) by considering several servers instead of one, each holding a copy of the database, and with the help of extra assumptions. Usually, to achieve (S)PIR, it is assumed that the servers cannot communicate with each other during and after the protocol ended (no-communication assumption), and that servers share randomness (in the symmetric case only). Examples of such protocols are:


* [[Multi-Database Quantum Symmetric Private Information Retrieval without Shared Randomness|Quantum multi-database SPIR protocols without shared randomness]] (replaced by prior shared entanglement between servers)
* [[Multi-Database Classical Symmetric Private Information Retrieval with Quantum Key Distribution|Classical multi-database SPIR protocols with QKD secured classical channels]]
* [[Multi-Database Quantum Symmetric Private Information Retrieval for Communicating and Colluding Servers|Multi-database quantum (S)PIR protocols for communicating and colluding servers]] – to do without the no-communication assumption
* [[Multi-Database Quantum Symmetric Private Information Retrieval for Coded Servers|Multi-database quantum (S)PIR protocols for coded servers]]