October 20, 2015
Collectively Witnessing Log Servers in CT
This document proposes a backward-compatible extension to CT enabling
log servers to obtain compact collective signatures from any number
of well-known "witness" servers, which clients can check without
gossip to verify that log server records have been widely witnessed.
Collective signatures proactively protect clients from man-in-the-
middle attackers who may have stolen the private keys of one or more
log servers, even if the attacker controls the client's network
access, the client is unwilling to gossip for privacy reasons, or the
client does not wish to incur the network bandwidth and/or latency
costs of gossip.