Web crawlers are the key component of services running on Internet and providing searching and indexing support for the entire Web, for corporate Intranets and large portal sites. More recently, crawlers have also bee...
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ISBN:
(纸本)9781424416851
Web crawlers are the key component of services running on Internet and providing searching and indexing support for the entire Web, for corporate Intranets and large portal sites. More recently, crawlers have also been used as tools to conduct focused Web searches and to gather data about the characteristics of the WWW. In this paper, we research on the gathering model of crawler in the distributed circumstance. We describe the function of every module and establish some rules which crawlers must follow to maintain the equilibrium load and robustness of system when they are searching on the web simultaneously. Then we design and implement a new URL assignment algorithm based on hash for partitioning the domain to crawl, and more in general discuss the complete decentralization of every task.
The Secure hash algorithm SHA-512 is a dedicated cryptographic hash function widely considered for use in data integrity assurance and data origin authentication security services. Reconfigurable hardware devices such...
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The Secure hash algorithm SHA-512 is a dedicated cryptographic hash function widely considered for use in data integrity assurance and data origin authentication security services. Reconfigurable hardware devices such as Field Programmable Gate Arrays (FPGAs) offer a flexible and easily upgradeable platform for implementation of cryptographic hash functions. Owing to the iterative structure of SHA-512, even a single transient error at any stage of the hash value computation will result in large number of errors in the final hash value. Hence, detection of errors becomes a key design issue. In this paper, we present a detailed analysis of the propagation of errors to the output in the hardware implementation of SHA-512. Included in this analysis are single, transient as well as permanent faults that may appear at any stage of the hash value computation. We then propose an error detection scheme based on parity codes and hardware redundancy. We report the performance metrics such as area, memory, and throughput for the implementation of SHA-512 with error detection capability on an FPGA of ALTERA. We achieved 100% fault coverage in the case of single faults with an area overhead of 21% and with a reduced throughput of 11.6% with the error detection circuit.
Voting is usually recognized as one of the main characteristics of Democracy. Electronic election is a very recent idea regarding voting. Voter, once given his vote, has to rely upon the election system's honesty ...
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ISBN:
(纸本)9781424415502
Voting is usually recognized as one of the main characteristics of Democracy. Electronic election is a very recent idea regarding voting. Voter, once given his vote, has to rely upon the election system's honesty and security. Free and fairness of an election is desired by almost everyone associated with it. Hence designing an election system needs special care. Furthermore, an electronic election should be more secure, transparent and trustworthy, as common people have less faith in computers due to system crashes and hacking threats. In this paper, we are going to describe our implementation of an efficient and secured electronic voting system based on the Fujioka-Okamoto-Ohta protocol which is the most practical and suitable protocol for large scale elections. Our implementation contains the automation of an online voting system providing some features which were absent in the previous implementations. We have made our system even more user friendly and secured but faster than the others using recent technologies and resources.
Packet classification by analyzing the traffic header information is an essential task of network processors. To efficiently store, retrieve and update information, key-based data accessing algorithms such as hashing ...
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ISBN:
(纸本)0780389247
Packet classification by analyzing the traffic header information is an essential task of network processors. To efficiently store, retrieve and update information, key-based data accessing algorithms such as hashing are usually used to improve the processing performance. In this paper, we propose the hybrid open hash, a composite algorithm that combines open addressing hash tables with the temporal responsiveness of incremental garbage collection. By dynamically switching between a novel table with increment;, construction via selective copying of used entries, and an aged table with incremental cleaning via emptying of deleted entries, this algorithm solves the structural problem of conventional open hashing due to remnants left by deleted keys. Thus, it increases the data accessing speed. We also implement and compare our algorithm with Brutil, the latest proposed hashing mechanism designed for real-time embedded systems, from the concurrency issue of multithreading to the performance simulation by taking the real traffic information to construct hashed keys. Our results show that hybrid open hash has better performance. Several possible enhancement approaches are also discussed to improve the performance further.
In recent years many chaotic cryptosystems based on Baptista's seminal work have been proposed. We analyze the security of two of the newest and most interesting ones, which use a dynamically updated look-up table...
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In recent years many chaotic cryptosystems based on Baptista's seminal work have been proposed. We analyze the security of two of the newest and most interesting ones, which use a dynamically updated look-up table and also work as stream ciphers. We provide different attack techniques to recover the keystream used by the algorithms. The knowledge of this keystream provides the attacker with the same information as the key and thus the security is broken. We also show that the dependence on the plaintext, and not on the key, of the look-up table updating mechanism facilitates cryptanalysis. (C) 2004 Elsevier B.V. All rights reserved.
Recently, we have proposed a fast chaotic cryptographic scheme based on iterating a logistic map with the look-up table updated dynamically. We found that after the whole encryption process, the final look-up table st...
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Recently, we have proposed a fast chaotic cryptographic scheme based on iterating a logistic map with the look-up table updated dynamically. We found that after the whole encryption process, the final look-up table strongly depends on the message and so it can be considered as its hash value or message authentication code. In this Letter, we generalize the chaotic cryptographic scheme so that it can perform both encryption and hashing to produce the cipher text as well as the hash value for a given message. The collision resistance of the proposed hashing approach is also analyzed. (C) 2002 Elsevier Science B.V. All rights reserved.
A new multicast group join/leave mechanism for mobile nodes (MNs) is proposed. The mechanism is based on hash algorithm. This paper explains the construction of a dynamic delivery tree of the mobile node movement for ...
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ISBN:
(纸本)0780381149
A new multicast group join/leave mechanism for mobile nodes (MNs) is proposed. The mechanism is based on hash algorithm. This paper explains the construction of a dynamic delivery tree of the mobile node movement for a multicast-based mobile IPv6 network, such that the branches of the tree constitute the shortest paths from the packet source to each of the visited locations. The branches of the tree grow and shrink to reach the mobile node when necessary. The mobile node is assigned a multicast address and the correspondent nodes (CNs) send packets to the multicast group. As the mobile node moves to a new location, it joins the multicast group through the new location and prunes through the old location. The performance of the proposed mechanism was evaluated through a simulation model built. or this purpose. Simulation results show that the dynamics of joining and leaving the group directly affect handoff latency and smoothness, as a result it conserve Radio Frequency (RF) bandwidth.
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