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松浦研究室のメンバー2025年4月現在一覧
メンバー紹介細井 琢朗
研究テーマ
Publications
abstract
If we want to realize a scientific approach to cybersecurity, we need objective
and reproducible evaluation of security. Although some of cryptographic
technologies have rigorous security proofs, a lot of cybersecurity technologies
rely on experimental evaluation which needs good datasets. One may expect that
sharing such datasets would help at least the reproducibility of the evaluation.
At the same time, one may be afraid that effective mechanism design is difficult
because there have been a lot of studies on disincentive problems
(e.g. free-riding) associated with information sharing in cybersecurity.
However, the requirements and typical solutions for data sharing would be
different from those for information sharing. In this paper, we comprehensively
discuss the features of "data sharing for cybersecurity research" based on a
systematic comparison with "information sharing for cybersecurity practice". We
also report a Japanese case in the field of malware analysis.
One important finding is that considering human resource development is an
important factor in the activities associated with data sharing.
abstract
When we want to realize a scientific approach to cybersecurity,
we need objective and reproducible evaluation of security properties.
Although some of cryptographic technologies have rigorous security proofs,
a lot of cybersecurity technologies rely on experimental security evaluation
which needs good datasets. One may expect that sharing such datasets would help
at least the reproducibility of the evaluation. At the same time, one may be afraid
that effective mechanism design is not trivial because there have been a lot of
studies on disincentive problems (e.g. free-riding) associated with information
sharing for cybersecurity practice. However, the requirements and typical solutions
for data sharing would be different from those for information sharing. In this poster,
we comprehensively discuss the features of data sharing for cybersecurity research
based on a systematic comparison with information sharing for cybersecurity practice.
We also identify some intrinsic limitations of the data sharing approach.
abstract
The mechanism of TCP retransmission timeout
is essential to the Internet congestion control.
But existing research pointed out
that this mechanism allows DoS attack
with low-rate mean traffic.
We proposed a change in TCP retransmission timeout management,
in which
length of TCP retransmission timer is increased
not to precisely twice of the prior timer length
in successive timeout waiting.
We investigate its effectiveness
in DoS attack mitigation analytically,
and some attack variants under this countermeasure.
田村 研輔
研究テーマ
Publications
abstract
Since cyber attacks such as cyberterrorism against Industrial
Control Systems (ICSs) and cyber espionage against companies managing
them have increased, the techniques to detect anomalies in early
stages are required. To achieve the purpose, several studies have developed
anomaly detection methods for ICSs. In particular, some techniques
using packet flow regularity in industrial control networks have achieved
high-accuracy detection of attacks disrupting the regularity, i.e. normal
behavior, of ICSs. However, these methods cannot identify scanning attacks
employed in cyber espionage because the probing packets assimilate
into a number of normal ones. For example, the malware called Havex is
customized to clandestinely acquire information from targeting ICSs using
general request packets. The techniques to detect such scanning attacks
using widespread packets await further investigation. Therefore, the goal of
this study was to examine high performance methods to identify anomalies
even if elaborate packets to avoid alert systems were employed for attacks
against industrial control networks. In this paper, a novel detection model
for anomalous packets concealing behind normal traffic in industrial control
networks was proposed. For the proposal of the sophisticated detection
method, we took particular note of packet flow regularity and employed the
Markov-chain model to detect anomalies. Moreover, we regarded not only
original packets but similar ones to them as normal packets to reduce false
alerts because it was indicated that an anomaly detection model using the
Markov-chain suffers from the ample false positives affected by a number
of normal, irregular packets, namely noise. To calculate the similarity between
packets based on the packet flow regularity, a vector representation
tool called word2vec was employed. Whilst word2vec is utilized for the
calculation of word similarity in natural language processing tasks, we applied
the technique to packets in ICSs to calculate packet similarity. As a
result, the Markov-chain with word2vec model identified scanning packets
assimilating into normal packets in higher performance than the conventional
Markov-chain model. In conclusion, employing both packet flow
regularity and packet similarity in industrial control networks contributes
to improving the performance of anomaly detection in ICSs.
島田 要
研究テーマ
Publications
張 一凡
研究テーマ
Publications
谷下 友一
研究テーマ
Publications
abstract
Updatable encryption (UE) allows a third-party server to update outsourced encrypted data without exposing keys and plaintexts.
The server can update ciphertexts to ones under a new key using an update token provided by the client.
UE can realize efficient key rotation and is effective against key compromise.
The standard security notions of UE capture the property that even if keys or update tokens are compromised, the confidentiality of messages is maintained by the key update and ciphertext update.
In general, the randomnesses used in the encryption and ciphertext update algorithms must be kept secret in the same way as the keys.
On the other hand, while key compromise is considered in existing security notions, randomness compromise is not.
In this paper, we define a new security notion for UE, IND-UE-R security, that is resilient to the compromise of randomnesses used to generate or update ciphertexts.
Furthermore, we prove that the UE construction RISE (EUROCRYPT'18) satisfies our proposed security notion.
abstract
Updatable encryption (UE) is a special type of symmetric-key encryption (SKE) that allows a third party to update ciphertexts while protecting plaintexts.
Alamati et al. (CRYPTO 2019) showed a curious connection between UE and public-key encryption (PKE) that PKE can be constructed from UE.
This implication result is somewhat surprising since it is well-known that PKE cannot be constructed from (ordinary) SKE in a black-box manner.
In this paper, we continue to study the relationships between UE and other cryptographic primitives to obtain further insights into the existence and power of UE, and assumptions required for it.
More specifically, we introduce some security properties that are natural to consider for UE (and are indeed satisfied by some existing UE schemes), and then investigate what types of public-key cryptographic primitives can be constructed from UE with the additional properties. Specifically, we show the following results:
- 2-round oblivious transfer (OT) can be constructed from UE that satisfies the \emph{oblivious samplability (OS)} of original ciphertexts (i.e. those generated by the ordinary encryption algorithm, as opposed to those generated by the ciphertext-update algorithm) and the OS of update tokens (that are used for updating ciphertexts).
- 3-round OT can be constructed from UE with OS of updated ciphertexts (i.e. those generated by the ciphertext-update algorithm).
- Lossy encryption and PKE secure against selective-opening attacks can be constructed from UE if it satisfies what we call \emph{statistical confidentiality of original ciphertexts}.
浅野 泰輝
研究テーマ
Publications
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