• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.16 no.1
• /
• pp.71-77
• /
• 2006

Several network attacks, such as distributed denial of service (DDoS) attack, present a very serious threat to the stability of the internet. The threat posed by network attacks on large networks, such as the internet, demands effective detection method. Therefore, a simple intrusion detection system on large-scale backbone network is needed for the sake of real-time detection, preemption and detection efficiency. In this paper, in order to discriminate attack traffic from legitimate traffic on backbone links, we suggest a relatively simple statistical measure, entropy, which can track value frequency. Den is conspicuous distinction of entropy values between attack traffic and legitimate traffic. Therefore, we can identify what kind of attack it is as well as detecting the attack traffic using entropy value.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.17 no.1
• /
• pp.33-39
• /
• 2007

Finite field multipliers are the basic building blocks in many applications such as error-control coding, cryptography and digital signal processing. Hence, the design of efficient dedicated finite field multiplier architectures can lead to dramatic improvement on the overall system performance. In this paper, a new bit serial structure for a multiplier with low latency in Galois field is presented. To speed up multiplication processing, we divide the product polynomial into several parts and then process them in parallel. The proposed multiplier operates standard basis of $GF(2^m)$ and is faster than bit serial ones but with lower area complexity than bit parallel ones. The most significant feature of the proposed architecture is that a trade-off between hardware complexity and delay time can be achieved.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.19 no.2
• /
• pp.31-38
• /
• 2009

To provide the privacy of a keyword, a public key encryption with keyword search(PEKS) firstly was propsed by Boneh et al. The PEKS scheme enables that an email sender sends an encrypted email with receiver's public key to an email server and a server can obtain the relation between the given encrypted email and an encrypted query generated by a receiver. In this email system, we easily consider the situation that a user sends the one identical encrypted email to multi-receiver like as group e-mail. Hwang and Lee proposed a searchable public key encryption considering multi-receivers. To reduce the size of transmission data and the server's computation is important issue in multi-receiver setting. In this paper, we propose an efficient searchable public key encryption for multi-receiver (mPEKS) which is more efficient and reduces the server's pairing computation.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.5 no.1
• /
• pp.37-50
• /
• 1995

The smart card with the cryptography and VLSI technologies makes it possible to implement the electronic cash easily. A number of electronic each schemes have been proposed by many cryptographic researchers. In this paper, we propose a practical electronic cash system, using blind digital signature scheme. Schnorr's authentication scheme based on the discrete logarithm problem, and the hierarchical cash tree based on two one-way hash functions for dividable payment. Thisf electronic cash scheme has such properties as privacy of the payment, off-line payment, non-reuseability of cash, transferability of cash to another customer, and dividable payment of cash. This electronic cash protocol is well suited for implementing in smart card.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.9 no.1
• /
• pp.103-114
• /
• 1999

Recently, various prototypes for electronic commerce are realized and its related researches are active under the present condition which it is increasing for the reality of its extended applications. First of all, actual demands are increasing for more secure and efficient electronic payment systems. Electronic cash, one of the Electronic payment systems, must have several properties like real money. Blind signature scheme by D. Chaum stands for the methods of obtaining privacy. In this paper, we propose a method for obtaining the blind signature based on the Elliptic Curve Cryptosystems, where the crytosystems are known as solving some problems of conventional crytosystems in views of computation time and key space. Also, we present a method for the divisibility of the electronic cash using our proposal by re-signing spare cash. Thus applying the proposed method, we can develop an efficient electronic payment systems.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.16 no.1
• /
• pp.55-63
• /
• 2006

Recently, there is much abnormal traffic driven by several worms, such as Nimda, Code Red, SQL Stammer, and so on, making badly severe damage to networks. Meanwhile, diverse prevention schemes for defeating abnormal traffic have been studied in the academic and commercial worlds. In this paper, we present the structure of a stepwise intrusion prevention system that is designed with the feature of putting limitation on the network bandwidth of each network traffic and dropping abnormal traffic, and then compare the proposed scheme with a pre-existing scheme, which is a True/False based an anomaly prevention scheme for several worm-patterns. There are two criteria for comparison of the schemes, which are Normal Traffic Rate (NTR) and False Positive Rate (FPR). Assuming that the abnormal traffic rate of a specific network is $\beta$ during a predefined time window, it is known that the average NTR of our stepwise intrusion prevention scheme increases by the factor of (1+$\beta$)/2 than that of True/False based anomaly prevention scheme and the average FPR of our scheme decrease by the factor of (1+$\beta$)/2.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.16 no.3
• /
• pp.17-28
• /
• 2006

The appearance of variant malicious codes using obfuscation techniques is accelerating the spread of malicious codes around the detection by a vaccine. n a system does not patch detection patterns for vulnerabilities and worms to the vaccine, it can be infected by the worms and malicious codes can be spreaded rapidly to other systems and networks in a few minute. Moreover, It is limited to the conventional pattern based detection and treatment for variants or new malicious codes. In this paper, we propose a method of behavior based detection by the static analysis, the dynamic analysis and the dynamic monitoring to detect a malicious code using obfuscation techniques with the PE compression. Also we show that dynamic monitoring can detect worms with the PE compression which accesses to important resources such as a registry, a cpu, a memory and files with the proposed method for similarity.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.16 no.6
• /
• pp.111-121
• /
• 2006

As Internet lastly grows, network attack techniques are transformed and new attack types are appearing. The existing network-based intrusion detection systems detect well known attack, but the false-positive or false-negative against unknown attack is appearing high. In addition, The existing network-based intrusion detection systems is difficult to real time detection against a large network pack data in the network and to response and recognition against new attack type. Therefore, it requires method to heighten the detection rate about a various large dataset and to reduce the false-positive. In this paper, we propose method to reduce the false-positive using multi-level detection algorithm, that is combine the multidimensional Apriori algorithm and the modified Negative Selection algorithm. And we apply this algorithm in intrusion detection and, to be sure, it has a good performance.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.19 no.6
• /
• pp.83-92
• /
• 2009

Ari Juels proposed Yoking-Proof protocol for authenticating multiple tags simultaneously using RFID system. Because common Yoking-Proof methods authenticate by using MAC (Message Authentication Code), it is difficult to apply them to inexpensive tags. It is also difficult to implement common hash functions such as MD5 in inexpensive tags. So, Ari Juels also proposed a lightweighted Yoking-Proof method with only 1 authentication. However, Minimalist MAC, which is a lightweighted MAC used in the proposed method is for single-use, and the proposed structure is vulnerable to replay attacks. Therefore, in this study, the minimalist MAC using Lamport's digital signature scheme was adopted, and a new type of Yoking-Proof protocol was proposed where it uses tags that are safe from replay attacks while being able to save multiple key values.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.21 no.1
• /
• pp.27-37
• /
• 2011

The IDS/IPS(Intrusion Detection/Prevention System) has been widely deployed to protect the internal network against internet attacks. Reducing the packet inspection time is one of the most important challenges of improving the performance of the IDS/IPS. Since the IDS/IPS needs to match multiple patterns for the incoming traffic, we may have to apply the multiple pattern matching schemes, some of which use finite automata, while the others use the shift table. In this paper, we first show that the performance of those schemes would degrade with various kinds of pattern sets and payload, and then propose a hybrid multiple pattern matching scheme which combines those two schemes. The proposed scheme is organized to guarantee an appropriate level of performance in any cases. The experimental results using real traffic show that the time required to do multiple pattern matching could be reduced effectively.