• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.6
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• pp.183-194
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• 2010

A company's private network protected by a firewall and NAT(Network Address Translation) is not accessible directly through an external internet. However, as Reverse Connection technology used by NetCat extends to the technologies such as SSH Tunnel or HTTP Tunnel, now anyone can easily access a private network of corporation protected by a firewall and NAT. Furthermore, while these kinds of technologies are commercially stretching out to various services such as a remote control and HTTP Tunnel, security managers in a company or general users are confused under the circumstances of inner or outer regulation which is not allowed to access to an internal system with a remote control. What is more serious is to make a covert channel invading a company's private network through a malicious code and all that technologies. By the way, what matters is that a given security system such as a firewall cannot shield from these perceived dangers. So, we analyze the indirect access of technological methods and the status quo about a company's internal network and find a solution to get rid of the related dangers.

• Convergence Security Journal
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• v.6 no.3
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• pp.59-67
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• 2006

Recently the Personal Computer hacking and game hacking for the purpose of gaining an economic profit is increased in Windows system. Malicious code often uses methods which inject dll or code into memory in target process for using covert channel for communicating among them, bypassing secure products like personal firewalls and obtaining sensitive information in system. This paper analyzes the technique for injecting and executing code into memory area in target process. In addition, this analyzes the PE format and IMPORT table for extracting injected dll in running process in affected system and describes a method for extracting and analyzing explicitly loaded dll files related with running process. This technique is useful for finding and analyzing infected processes in affected system.

• Journal of Korea Multimedia Society
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• v.15 no.7
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• pp.891-902
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• 2012

Reversible data hiding scheme is a form of steganography in which the secret embedding data can be retrieved from a stego image for the purpose of identification, copyright protection and making a covert channel. The reversible data hiding should satisfy that not only are the distortions due to artifacts against the cover image invisible but also it has large embedding capacity as far as possible. In this paper, we propose a robust reversible data hiding scheme by exploiting the differences between a center pixel and its neighboring pixels in each sub-block of the image to embed secret data into extra space. Moreover, our scheme enhances the embedding capacity and can recover the embedded data from the stego image without causing any perceptible distortions to the cover image. Simulation results show that our proposed scheme has lower visible distortions in the stego image and provides robustness to geometrical image manipulations, such as rotation and cropping operations.

• The Transactions of the Korea Information Processing Society
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• v.4 no.3
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• pp.659-669
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• 1997

Security as weel as consistency of data is very important issue in databaed security.This the serializability of transactions must be maintained and particularly covert channel not caesed between a high-level transaction and a low- level one.In this paper, we propose a secure transaction management algorithm using synamic version control] method that can slove disk space overhead to maintain multiversion and the problem that reansactions read too old versions when two versions are maintained.Disk space overhead can be sloved by properly cerating versions and synamically maintaining the number of versions and the problem for reading too old version can be solved by having transactions read versions as recent as possible.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.11
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• pp.5588-5613
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• 2018

Virtualization technology has been widely applied in the area of computer security research that provides a new method for system protection. It has been a hotspot in system security research at present. Virtualization technology brings new risk as well as progress to computer operating system (OS). A multi-level perception security model using virtualization is proposed to deal with the problems of over-simplification of risk models, unreliable assumption of secure virtual machine monitor (VMM) and insufficient integration with virtualization technology in security design. Adopting the enhanced isolation mechanism of address space, the security perception units can be protected from risk environment. Based on parallel perceiving by the secure domain possessing with the same privilege level as VMM, a mechanism is established to ensure the security of VMM. In addition, a special pathway is set up to strengthen the ability of information interaction in the light of making reverse use of the method of covert channel. The evaluation results show that the proposed model is able to obtain the valuable risk information of system while ensuring the integrity of security perception units, and it can effectively identify the abnormal state of target system without significantly increasing the extra overhead.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.11 no.1
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• pp.43-54
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• 2001

In this paper we study the use of polyinstantiation for spatial data, for the purpose of solving cover in topology channel in multilevel secure spatial database systems. Spatial database system with topological structure has a number of spatial analysis function using spatial data and neighbored one\`s each other. But. it has problems that information flow is occurred by topological relationship in spatial database systems. Geographic Information System(CIS) must be needed mandatory access control because there ,are many information flow through positioning information And topological relationship between spatial objects. Moreover, most GIS applications also graphe user interface(GUI). In addressing these problems, we design the MLS/SRDM(Multi Level Security/Spatial Relational Data Model) and propose polyinstantiation for spatial data for solving information flow that occurred by toplogical relationship of spatial data.

• Journal of KIISE:Software and Applications
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• v.26 no.8
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• pp.955-963
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• 1999

다단계 보안 실시간 데이타베이스 시스템은 데이타베이스의 일관성 유지와 실시간 요구인 마감시간의 만족, 그리고 기밀성을 띤 데이타가 노출될 수 있는 비밀채널(covert-channel)의 방지라는 요구사항을 모두 만족해야 한다. 기존의 SRT-2PL(Secure Real-Time 2 Phase Locking)은 원본과 복사본으로 데이타 객체를 분리시켜 다른 등급간에 불간섭(non-interference)을 유지하여 비밀채널의 방지를 가능하게 하였으나, 복사본이 모든 데이타 객체에 대해 항상 존재하므로 메모리의 낭비가 있을 수 있고, 복사본의 갱신을 위한 갱신 큐의 관리에 따르는 오버헤드와 그에 따른 예측성 결여라는 문제점을 갖고 있다. 이를 개선하기 위하여 본 논문에서는 다단계 보안 실시간 데이타베이스 시스템의 요구사항을 모두 만족하는 동적 복사 프로토콜을 제안한다. 동적 복사 프로토콜은 로킹 기법을 기초로 동작하고, 트랜잭션의 작업에 따라 동적으로 복사본을 생성하고 삭제한다. 모의 실험 결과 제안한 동적 복사 프로토콜은 비밀채널을 방지하고 동적인 복사본의 생성으로 SRT-2PL의 단점인 메모리 낭비를 줄일 수 있으며, 예측성을 높여 마감시간 오류율을 감소시켰다.Abstract Concurrency control of real-time secure database system must satisfy not only logical data consistency but also timing constraints and security requirements associated with transactions. These conflicting natures between timing constraints and security requirements are often resolved by maintaining several versions(or secondary copies) on the same data items. In this paper, we propose a new lock-based concurrency control protocol, Dynamic Copy Security Protocol, ensuring both two conflicting requirements. Our protocol aims for reducing the storage overhead of maintaining secondary copies and minimizing the processing overhead of update history. Main idea of our protocol is to keep a secondary copy only when it is needed to resolve the conflicting read/write operations in real time secure database systems. For doing this, a secondary copy is dynamically created and removed during a transaction's read/write operations according to our protocol. We have also examined the performance characteristics of our protocol through simulation under different workloads while comparing the existing real time security protocol. The results show that our protocol consumed less storage and decreased the missing deadline transactions.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.4
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• pp.739-751
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• 2019

Security in embedded devices has become a significant issue. Threats on the sup-ply chain, like using counterfeit components or inserting backdoors intentionally are one of the most significant issues in embedded devices security. To mitigate these threats, high-level security evaluation and certification more than EAL (Evaluation Assurance Level) 5 on CC (Common Criteria) are necessary on hardware components, especially on the cryptographic module such as AES. High-level security evaluation and certification require detecting covert channel such as backdoors on the cryptographic module. However, previous studies have a limitation that they cannot detect some kinds of backdoors which leak the in-formation recovering a secret key on the cryptographic module. In this paper, we present an expanded definition of backdoor on hardware AES module and show how to detect the backdoor which is never detected in Verilog HDL using model checker NuSMV.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.9 no.1
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• pp.15-28
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• 1999

In Multilevel Secure Database Management System(MLS/DBMS), we assume that system has a security clearance level for each user and a classification level for each data item in system and the objective of these systems is to protect secure information from unauthorized user. Many algorithms which have been researched have focus on removing covert channel by modifying conventional lock-based algorithm or timestamp-based algorithm. but there is high-level starvation problem that high level transaction is aborted by low level transaction repeatedly. In order to solve this problem, we propose an algorithm to reduce high-level starvation using dynamic adjustment of serialization order, which is basically using orange lock. Because our algorithm is based on a single version unlike conventional secure algorithms which are performed on multiversion, it can get high degree of concurrency control. we also show that it guarantees the serializability of concurrent execution, and satisfies secure properties of MLS/DBMS.