1,902 research outputs found
Cryptographic enforcement of information flow policies without public information via tree partitions
We may enforce an information flow policy by encrypting a protected resource
and ensuring that only users authorized by the policy are able to decrypt the
resource. In most schemes in the literature that use symmetric cryptographic
primitives, each user is assigned a single secret and derives decryption keys
using this secret and publicly available information. Recent work has
challenged this approach by developing schemes, based on a chain partition of
the information flow policy, that do not require public information for key
derivation, the trade-off being that a user may need to be assigned more than
one secret. In general, many different chain partitions exist for the same
policy and, until now, it was not known how to compute an appropriate one.
In this paper, we introduce the notion of a tree partition, of which chain
partitions are a special case. We show how a tree partition may be used to
define a cryptographic enforcement scheme and prove that such schemes can be
instantiated in such a way as to preserve the strongest security properties
known for cryptographic enforcement schemes. We establish a number of results
linking the amount of secret material that needs to be distributed to users
with a weighted acyclic graph derived from the tree partition. These results
enable us to develop efficient algorithms for deriving tree and chain
partitions that minimize the amount of secret material that needs to be
distributed.Comment: Extended version of conference papers from ACNS 2015 and DBSec 201
ANCHOR: logically-centralized security for Software-Defined Networks
While the centralization of SDN brought advantages such as a faster pace of
innovation, it also disrupted some of the natural defenses of traditional
architectures against different threats. The literature on SDN has mostly been
concerned with the functional side, despite some specific works concerning
non-functional properties like 'security' or 'dependability'. Though addressing
the latter in an ad-hoc, piecemeal way, may work, it will most likely lead to
efficiency and effectiveness problems. We claim that the enforcement of
non-functional properties as a pillar of SDN robustness calls for a systemic
approach. As a general concept, we propose ANCHOR, a subsystem architecture
that promotes the logical centralization of non-functional properties. To show
the effectiveness of the concept, we focus on 'security' in this paper: we
identify the current security gaps in SDNs and we populate the architecture
middleware with the appropriate security mechanisms, in a global and consistent
manner. Essential security mechanisms provided by anchor include reliable
entropy and resilient pseudo-random generators, and protocols for secure
registration and association of SDN devices. We claim and justify in the paper
that centralizing such mechanisms is key for their effectiveness, by allowing
us to: define and enforce global policies for those properties; reduce the
complexity of controllers and forwarding devices; ensure higher levels of
robustness for critical services; foster interoperability of the non-functional
property enforcement mechanisms; and promote the security and resilience of the
architecture itself. We discuss design and implementation aspects, and we prove
and evaluate our algorithms and mechanisms, including the formalisation of the
main protocols and the verification of their core security properties using the
Tamarin prover.Comment: 42 pages, 4 figures, 3 tables, 5 algorithms, 139 reference
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