Although the Internet has become a pervasive social infrastructure that is indispensable to people’s lives, various security issues have arisen, including cyber attacks that malfunction specific Web servers and cache servers, and the theft of privacy information such as highly confidential personal data.
Therefore, we are conducting research on network security technologies to enable people to use network services safely and comfortably, focusing on the following themes.
Prevention Techniques for Cache Contamination Attack
In order to provide comfortable web browsing and video streaming services, cache distribution is widely used, where cache servers are installed at various locations on the network, and data is distributed from cache servers located near the user.
To increase the effectiveness of caching, popular content is prioritized for storage on cache servers. However, the problem of cache pollution attacks, in which malicious users intentionally make numerous requests for low-popular content, thereby reducing the effectiveness of caching, has been pointed out.
Moreover, in Information-Centric Networks (ICNs), which are expected to be the network of the future, everyone can upload content over the network, so the problem of content poisoning attacks reducing the effect of caches by injecting meaningless contents into routers’ caches has been identified.
To this end, we are investigating low-cost detection and prevention techniques for cache contamination attacks using the blockchain and probabilistic data structures such as the Bloom filter.
Detecting DDoS Attacks Tricking CDN Cache Servers
Since a DDoS attack is an attack that places an enormous load on the target server, if content is delivered using a CDN, the load is distributed and a DDoS attack is not possible. However, a DDoS attack can be established when an attacker fakes the IP address of a cache server as the origin address and sends attack packets from bots to the IP address of the origin server.
Therefore, we are working on a DDoS attack detection technique that combines time-series analysis of packet arrival intervals and DNS log inspection.
Prevention Techniques for Crossfire Attack
The threat of crossfire attacks that disrupt the services of servers in the attack area by injecting attack traffic into links that connect to specific areas of the network and overloading them has been pointed out.
To prevent crossfire attack, we have focused on the behavior of attackers who send traceroute messages to many servers in the attack area from many bots in the preparation stage of crossfire attacks and investigated method of detecting crossfire attack based on the interval of traceroute messages.
Access Control of Information-Centric Networking
For content with a limited number of users, such as paid content, access control is required to determine whether or not request can be accepted. In the Internet, delivery requests always reach servers of content providers, so access control is possible at servers of content providers. However, in the Information-Centric Networking (ICN), content is cached and delivered from routers, so content requests do not always reach content providers, so access control is difficult in ICN.
To this end, we are investigating access control schemes in ICN that combine public-key cryptography and symmetric-key cryptography.
Information Management Techniques Using Blockchain
Although a huge amount of data is managed at a centralized single location traditionally, vulnerability to failure and attack is an issue. Using distributed management techniques that manage data in multiple locations solves these issues. However, security risks such as data tampering and unauthorized access will increase.
Therefore, blockchain is attracting attention as a distributed data management technology that is difficult to tamper with. Our laboratory is conducting research on the use of blockchain to manage personal and other information that can be made public.
Privacy-Preserving Crosschain communication Over Multiple Blockchains
Cross-chain communication, in which virtual currencies and other currencies are exchanged between multiple different blockchains, is attracting attention. However, the challenge is to establish a technology to prove the legitimacy of different blockchains while protecting their privacy.
Therefore, this laboratory is working on the realization of cross-chain communication that protects privacy and reduces the amount of data exchanged by using a hierarchical structure in which multiple blockchains are bound together by a parent blockchain, using a cryptographic scheme called commitment scheme.