939 research outputs found
The Crypto-democracy and the Trustworthy
In the current architecture of the Internet, there is a strong asymmetry in
terms of power between the entities that gather and process personal data
(e.g., major Internet companies, telecom operators, cloud providers, ...) and
the individuals from which this personal data is issued. In particular,
individuals have no choice but to blindly trust that these entities will
respect their privacy and protect their personal data. In this position paper,
we address this issue by proposing an utopian crypto-democracy model based on
existing scientific achievements from the field of cryptography. More
precisely, our main objective is to show that cryptographic primitives,
including in particular secure multiparty computation, offer a practical
solution to protect privacy while minimizing the trust assumptions. In the
crypto-democracy envisioned, individuals do not have to trust a single physical
entity with their personal data but rather their data is distributed among
several institutions. Together these institutions form a virtual entity called
the Trustworthy that is responsible for the storage of this data but which can
also compute on it (provided first that all the institutions agree on this).
Finally, we also propose a realistic proof-of-concept of the Trustworthy, in
which the roles of institutions are played by universities. This
proof-of-concept would have an important impact in demonstrating the
possibilities offered by the crypto-democracy paradigm.Comment: DPM 201
On Borrowed Time -- Preventing Static Power Side-Channel Analysis
In recent years, static power side-channel analysis attacks have emerged as a
serious threat to cryptographic implementations, overcoming state-of-the-art
countermeasures against side-channel attacks. The continued down-scaling of
semiconductor process technology, which results in an increase of the relative
weight of static power in the total power budget of circuits, will only improve
the viability of static power side-channel analysis attacks. Yet, despite the
threat posed, limited work has been invested into mitigating this class of
attack. In this work we address this gap. We observe that static power
side-channel analysis relies on stopping the target circuit's clock over a
prolonged period, during which the circuit holds secret information in its
registers. We propose Borrowed Time, a countermeasure that hinders an
attacker's ability to leverage such clock control. Borrowed Time detects a
stopped clock and triggers a reset that wipes any registers containing
sensitive intermediates, whose leakages would otherwise be exploitable. We
demonstrate the effectiveness of our countermeasure by performing practical
Correlation Power Analysis attacks under optimal conditions against an AES
implementation on an FPGA target with and without our countermeasure in place.
In the unprotected case, we can recover the entire secret key using traces from
1,500 encryptions. Under the same conditions, the protected implementation
successfully prevents key recovery even with traces from 1,000,000 encryptions
Effects of Architecture on Information Leakage of a Hardware Advanced Encryption Standard Implementation
Side-channel analysis (SCA) is a threat to many modern cryptosystems. Many countermeasures exist, but are costly to implement and still do not provide complete protection against SCA. A plausible alternative is to design the cryptosystem using architectures that are known to leak little information about the cryptosystem\u27s operations. This research uses several common primitive architectures for the Advanced Encryption Standard (AES) and assesses the susceptibility of the full AES system to side-channel attack for various primitive configurations. A combined encryption/decryption core is also evaluated to determine if variation of high-level architectures affects leakage characteristics. These different configurations are evaluated under multiple measurement types and leakage models. The results show that different hardware configurations do impact the amount of information leaked by a device, but none of the tested configurations are able to prevent exploitation
Keeping Authorities "Honest or Bust" with Decentralized Witness Cosigning
The secret keys of critical network authorities - such as time, name,
certificate, and software update services - represent high-value targets for
hackers, criminals, and spy agencies wishing to use these keys secretly to
compromise other hosts. To protect authorities and their clients proactively
from undetected exploits and misuse, we introduce CoSi, a scalable witness
cosigning protocol ensuring that every authoritative statement is validated and
publicly logged by a diverse group of witnesses before any client will accept
it. A statement S collectively signed by W witnesses assures clients that S has
been seen, and not immediately found erroneous, by those W observers. Even if S
is compromised in a fashion not readily detectable by the witnesses, CoSi still
guarantees S's exposure to public scrutiny, forcing secrecy-minded attackers to
risk that the compromise will soon be detected by one of the W witnesses.
Because clients can verify collective signatures efficiently without
communication, CoSi protects clients' privacy, and offers the first
transparency mechanism effective against persistent man-in-the-middle attackers
who control a victim's Internet access, the authority's secret key, and several
witnesses' secret keys. CoSi builds on existing cryptographic multisignature
methods, scaling them to support thousands of witnesses via signature
aggregation over efficient communication trees. A working prototype
demonstrates CoSi in the context of timestamping and logging authorities,
enabling groups of over 8,000 distributed witnesses to cosign authoritative
statements in under two seconds.Comment: 20 pages, 7 figure
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
A Standalone FPGA-based Miner for Lyra2REv2 Cryptocurrencies
Lyra2REv2 is a hashing algorithm that consists of a chain of individual
hashing algorithms, and it is used as a proof-of-work function in several
cryptocurrencies. The most crucial and exotic hashing algorithm in the
Lyra2REv2 chain is a specific instance of the general Lyra2 algorithm. This
work presents the first hardware implementation of the specific instance of
Lyra2 that is used in Lyra2REv2. Several properties of the aforementioned
algorithm are exploited in order to optimize the design. In addition, an
FPGA-based hardware implementation of a standalone miner for Lyra2REv2 on a
Xilinx Multi-Processor System on Chip is presented. The proposed Lyra2REv2
miner is shown to be significantly more energy efficient than both a GPU and a
commercially available FPGA-based miner. Finally, we also explain how the
simplified Lyra2 and Lyra2REv2 architectures can be modified with minimal
effort to also support the recent Lyra2REv3 chained hashing algorithm.Comment: 13 pages, accepted for publication in IEEE Trans. Circuits Syst. I.
arXiv admin note: substantial text overlap with arXiv:1807.0576
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