• 대한임베디드공학회논문지
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• 제11권6호
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• pp.335-341
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• 2016

As information technology advances rapidly, various smart devices are becoming an essential element in our lives. Smart devices are providing services to users through applications up on the operating system. Operating systems have a variety of rules, such as scheduling applications and controlling hardwares. Among those rules, it is significant to protect private information in the information-oriented society. Therefore, isolation task, that makes certain memory space separated for each application, should highly be guaranteed. However, modern operating system offers the function to access the memory space from other applications for the sake of debugging. If this ability is misused, private information can be leaked or modified. Even though the access authority to memory is strictly managed, there exist cases found exploited. In this paper, we analyze the problems of the function provided in the Android environment that is the most popular and opened operating system. Also, we discuss how to avoid such kind of problems and verify with experiments.

• IMMUNE NETWORK
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• 제23권1호
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• pp.11.1-11.11
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• 2023

Memory T cells that mediate fast and effective protection against reinfections are usually generated upon recognition on foreign Ags. However, a "memory-like" T-cell population, termed virtual memory T (T_VM) cells that acquire a memory phenotype in the absence of foreign Ag, has been reported. Although, like innate cells, T_VM cells reportedly play a role in first-line defense to bacterial or viral infections, their protective or pathological roles in immune-related diseases are largely unknown. In this review, we discuss the current understanding of T_VM cells, focusing on their distinct characteristics, immunological properties, and roles in various immune-related diseases, such as infections and cancers.

• 대한임베디드공학회논문지
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• 제17권1호
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• pp.59-65
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• 2022

Virtual memory is used as the method to ensure the safety of the system through memory protection in the real-time system. TLB miss caused by using virtual memory makes the real-time system WCET more pessimistically. TLB lockdown can be applied as a method to improve this problem. However, processors with limited TLB lockdown entries, a selection criterion is needed to efficiently utilize the TLB lockdown entry. In this paper, the most frequently accessed virtual pages in the process are applied to the TLB lockdown by analyzing memory profiling. The results showed that micro data TLB miss stall cycle and main data TLB miss stall cycle of the processor decreased by at least 4.7% and up to 29.7%.

• 인터넷정보학회논문지
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• 제17권6호
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• pp.93-101
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• 2016

안드로이드 폰이 점점 대중화됨에 따라 많은 어플리케이션이 제작자의 이윤과 직결되는 데이터나 스마트 폰 사용자의 민감한 데이터를 다룬다. 이러한 중요 데이터는 당연히 보호받아야 하지만 안드로이드에서는 악의적인 사용자에 의해 조작되거나 공격자에 의해 유출될 수 있다. 이런 일이 발생하는 이유는 안드로이드의 근간인 리눅스의 디버깅 기능이 악용되기 때문이다. 리눅스의 디버깅 기능을 이용하면 다른 어플리케이션의 가상 메모리에 접근하는 것이 가능하다. 이 기능이 악용되는 것을 방지하기 위해선 해당 기능을 제공하는 주체인 리눅스의 커널에서 기존의 접근 제어를 더욱 강화해야 한다. 하지만 현재 이 기능은 안드로이드 환경의 특성을 반영하지 않은 채 기존의 리눅스와 동일한 접근 제어를 사용하고 있다. 이에 본 논문에서는 리눅스가 제공하는 다른 어플리케이션의 가상 메모리에 접근할 수 있는 기능을 분석하고, 분석 결과와 안드로이드 환경을 고려하여 스레드 그룹 ID를 검증하는 새로운 계층을 추가하는 방안을 제시한다. 이 방안을 적용함으로써 접근 제어를 더욱 강화할 수 있다. 실제로 본 논문이 제안한 방법이 접근 제어를 강화할 수 있는 지 확인하기 위해, 다른 어플리케이션의 메모리를 수정할 수 있는 메모리 조작 어플리케이션으로 자체 제작한 어플리케이션의 데이터 수정을 시도한다. 접근 제어를 강화하기 전에는 메모리 조작 어플리케이션이 자체 제작한 어플리케이션의 메모리에 있는 데이터를 수정할 수 있었지만, 접근 제어를 강화한 후에는 데이터 수정에 실패하는 것을 확인할 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.2276-2291
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• 2017

Data protection of removable storage devices is an important issue in information security. Unfortunately, most existing data protection mechanisms are aimed at protecting computer platform which is not suitable for ultra-low-power devices. To protect the flash disk appropriately and efficiently, we propose a trust based USB flash disk, named UTrustDisk. The data protection technologies in UTrustDisk include data authentication protocol, data confidentiality protection and data leakage prevention. Usually, the data integrity protection scheme is the bottleneck in the whole system and we accelerate it by WH universal hash function and speculative caching. The speculative caching will cache the potential hot chunks for reducing the memory bandwidth pollution. We adopt the symmetric encryption algorithm to protect data confidentiality. Before mounting the UTrustDisk, we will run a trusted virtual domain based lightweight virtual machine for preventing information leakage. Besides, we prove formally that UTrustDisk can prevent sensitive data from leaking out. Experimental results show that our scheme's average writing throughput is 44.8% higher than that of NH scheme, and 316% higher than that of SHA-1 scheme. And the success rate of speculative caching mechanism is up to 94.5% since the access pattern is usually sequential.