Title: Multiparty Computation Secure Against
Continual Memory Leakage

Abstract:

Secure multiparty computation (MPC) is a means for mutually 
distrusting parties to evaluate functions on their secret 
inputs, while revealing nothing beyond the function outputs.  
We construct an MPC protocol that is secure even 
if a malicious adversary, in addition to corrupting (1- \epsilon) 
fraction of all parties for an arbitrarily small constant \epsilon > 0, 
can leak information about the secret state of each honest 
party. This leakage can be continuous for an unbounded 
number of executions of the MPC protocol, computing different 
functions on the same or different set of inputs. We assume 
a (necessary) "leak-free" preprocessing stage.

We emphasize that we achieve leakage resilience without
weakening the security guarantee of classical MPC. Namely,
an adversary who is given leakage on honest parties' states,
is guaranteed to learn nothing beyond the input and output
values of corrupted parties. This is in contrast with previous
works on leakage in the multi-party protocol setting,
which weaken the security notion, and only guarantee that a
protocol which leaks \lambda bits about the parties' secret states,
yields at most \lambda bits of leakage on the parties' private in-
puts. For some functions, such as voting, such leakage can
be detrimental.

Our result relies on standard cryptographic assumptions,
and our security parameter is polynomially related to the
number of parties.