  Anonymity in networked communication is vital for many privacy-preserving
tasks. Secure key distribution alone is insufficient for high-security
communications, often knowing who transmits a message to whom and when must
also be kept hidden from an adversary. Here we experimentally demonstrate 5
information-theoretically secure anonymity protocols on an 8 user city-wide
quantum network using polarisation-entangled photon pairs. At the heart of
these protocols is anonymous broadcasting, which is a cryptographic primitive
that allows one user to reveal one bit of information while keeping her
identity anonymous. For a network of $n$ users, the protocols retain anonymity
for the sender, given less than $n-2$ users are dishonest. This is one of the
earliest implementations of genuine multi-user cryptographic protocols beyond
standard QKD. Our anonymous protocols enhance the functionality of any
fully-connected Quantum Key Distribution network without trusted nodes.
