  Dining-cryptographers networks (DCN) can achieve information-theoretical
privacy. Unfortunately, they are not well suited for peer-to-peer networks as
they are used in blockchain applications to disseminate transactions and blocks
among participants. In previous but preliminary work, we proposed a threephase
approach with an initial phase based on a DCN with a group size of k while
later phases take care of the actual broadcast within a peer-to-peer network.
This paper describes our DCN protocol in detail and adds a performance
evaluation powered by our proof-of-concept implementation. Our contributions
are (i) an extension of the DCN protocol by von Ahn for fair delivery of
arbitrarily long messages sent by potentially multiple senders, (ii) a privacy
and security analysis of this extension, (iii) various performance optimisation
especially for best-case operation, and (iv) a performance evaluation. The
latter uses a latency of 100 ms and a bandwidth limit of 50 Mbit/s between
participants. The interquartile range of the largest test of the highly secured
version took 35s+-1.25s for a full run. All tests of the optimized common-case
mode show the dissemination of a message within 0.5s+-0.1s. These results
compare favourably to previously established protocols for k-anonymous
transmission of fixed size messages, outperforming the original protocol for
messages as small as 2 KiB.
