Method for constructing alphabet compression based extend finite automaton

A technology of limited automata and automatic mechanism, which is applied in the direction of electrical digital data processing, special data processing applications, instruments, etc., to achieve the effect of fast storage, ensuring matching efficiency and reducing storage space

Inactive Publication Date: 2011-08-17
HUNAN UNIV
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  • Application Information

AI Technical Summary

Problems solved by technology

The DFA based on the alphabet compression compresses the storage space, but needs to pay the price of querying the alphabet compression table

Method used

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  • Method for constructing alphabet compression based extend finite automaton
  • Method for constructing alphabet compression based extend finite automaton
  • Method for constructing alphabet compression based extend finite automaton

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Embodiment Construction

[0029] In order to facilitate the description of the algorithm, some relevant definitions are introduced first. Letters a and b are said to be equivalent to state S when state S leads to the same next state for letters a and b. like figure 1As shown, state S0 leads to the same next state S2 for both letters b and c, therefore, letters b and c are equivalent for state S0. State S1 reaches a different next state for letters b and c, then letters b and c are not equivalent for state S1. When a subset of the alphabet is equivalent to all states of a state set, we call this subset of the alphabet the alphabetic equivalence class of the state set. like figure 1 As shown, the alphabet subset {B, b, C, c} is the alphabetic equivalence class of the state set {S0, S2, S5, S6}.

[0030] We can divide the XFA alphabet into a set of letter equivalence classes to generate an alphabet compression table (ACT, Alphabet Compression Table). Each XFA state requires only one migration edge fo...

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Abstract

The invention discloses a method for constructing an alphabet compression based extend finite automaton (ACFA). The method comprises the following steps of: checking and testing in the alphabet compression based extend finite automaton by selecting a proper rule set; reading in the rule set, constructing a finite automaton by the method for constructing the alphabet compression based extend finite automaton and generating a state set at the same time; and dividing the alphabet of each state set by a method for matching the alphabet compression based extend finite automaton and compressing a migration table of the alphabet. Compared with an extend finite automaton (XFA), the migration edge of the ACFA is reduced by 95.6 percent, the storage space of the ACFA is reduced by 90.7 percent, and the matching time of the ACFA is only increased by 23.6 percent; therefore, the ACFA is a quick regular expression matching method with efficient storing performance. Compared with the conventional regular expression matching method, the ACFA is particularly applicable for detection of a high-speed depth packet.

Description

technical field [0001] The invention relates to electronic computer network technology, in particular to an extended finite automaton construction method based on alphabet compression. Background technique [0002] The feature matching algorithm is the key to deep packet inspection. It scans the data packets and identifies the data packets that match the feature rule set. In order to identify all matching features in one scan, deep packet inspection generally uses a multi-pattern matching algorithm. [0003] As attacks become more and more complex, such as evasion attacks, variant attacks, etc., it is difficult for precise character strings to accurately describe complex attack characteristics. At the same time, the precise string will cause a large number of false positive alarms in the network intrusion detection system. Due to the flexibility and high efficiency of regular expressions, many security products currently use regular expressions instead of exact strings to ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/30H04L29/08H04L29/06
Inventor 张大方金军航黄昆
Owner HUNAN UNIV
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