1,214 research outputs found
Certificate-Based Encryption Without Random Oracles
We present a certificate-based encryption scheme which is fully secure in the standard model. Our
scheme is based on the identity-based encryption scheme of Waters \cite{W05}. Although some
generic constructions from IBE to CBE has been previously proposed, they use the Random Oracle
heuristic or provide less practical schemes than ours. Finally, we point out that one of
the existing generic constructions going from IBE to CBE is flawed
Stacco: Differentially Analyzing Side-Channel Traces for Detecting SSL/TLS Vulnerabilities in Secure Enclaves
Intel Software Guard Extension (SGX) offers software applications enclave to
protect their confidentiality and integrity from malicious operating systems.
The SSL/TLS protocol, which is the de facto standard for protecting
transport-layer network communications, has been broadly deployed for a secure
communication channel. However, in this paper, we show that the marriage
between SGX and SSL may not be smooth sailing.
Particularly, we consider a category of side-channel attacks against SSL/TLS
implementations in secure enclaves, which we call the control-flow inference
attacks. In these attacks, the malicious operating system kernel may perform a
powerful man-in-the-kernel attack to collect execution traces of the enclave
programs at page, cacheline, or branch level, while positioning itself in the
middle of the two communicating parties. At the center of our work is a
differential analysis framework, dubbed Stacco, to dynamically analyze the
SSL/TLS implementations and detect vulnerabilities that can be exploited as
decryption oracles. Surprisingly, we found exploitable vulnerabilities in the
latest versions of all the SSL/TLS libraries we have examined.
To validate the detected vulnerabilities, we developed a man-in-the-kernel
adversary to demonstrate Bleichenbacher attacks against the latest OpenSSL
library running in the SGX enclave (with the help of Graphene) and completely
broke the PreMasterSecret encrypted by a 4096-bit RSA public key with only
57286 queries. We also conducted CBC padding oracle attacks against the latest
GnuTLS running in Graphene-SGX and an open-source SGX-implementation of mbedTLS
(i.e., mbedTLS-SGX) that runs directly inside the enclave, and showed that it
only needs 48388 and 25717 queries, respectively, to break one block of AES
ciphertext. Empirical evaluation suggests these man-in-the-kernel attacks can
be completed within 1 or 2 hours.Comment: CCS 17, October 30-November 3, 2017, Dallas, TX, US
Anonymous and Adaptively Secure Revocable IBE with Constant Size Public Parameters
In Identity-Based Encryption (IBE) systems, key revocation is non-trivial.
This is because a user's identity is itself a public key. Moreover, the private
key corresponding to the identity needs to be obtained from a trusted key
authority through an authenticated and secrecy protected channel. So far, there
exist only a very small number of revocable IBE (RIBE) schemes that support
non-interactive key revocation, in the sense that the user is not required to
interact with the key authority or some kind of trusted hardware to renew her
private key without changing her public key (or identity). These schemes are
either proven to be only selectively secure or have public parameters which
grow linearly in a given security parameter. In this paper, we present two
constructions of non-interactive RIBE that satisfy all the following three
attractive properties: (i) proven to be adaptively secure under the Symmetric
External Diffie-Hellman (SXDH) and the Decisional Linear (DLIN) assumptions;
(ii) have constant-size public parameters; and (iii) preserve the anonymity of
ciphertexts---a property that has not yet been achieved in all the current
schemes
Average-Case Complexity
We survey the average-case complexity of problems in NP.
We discuss various notions of good-on-average algorithms, and present
completeness results due to Impagliazzo and Levin. Such completeness results
establish the fact that if a certain specific (but somewhat artificial) NP
problem is easy-on-average with respect to the uniform distribution, then all
problems in NP are easy-on-average with respect to all samplable distributions.
Applying the theory to natural distributional problems remain an outstanding
open question. We review some natural distributional problems whose
average-case complexity is of particular interest and that do not yet fit into
this theory.
A major open question whether the existence of hard-on-average problems in NP
can be based on the PNP assumption or on related worst-case assumptions.
We review negative results showing that certain proof techniques cannot prove
such a result. While the relation between worst-case and average-case
complexity for general NP problems remains open, there has been progress in
understanding the relation between different ``degrees'' of average-case
complexity. We discuss some of these ``hardness amplification'' results
- …