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Hackers can sniff the WLAN after preparing these works. Because WLAN’s data are transmitted in the air, Hackers can easily get data they want. Such as: AP name, SSID and MAC address[3]. They can break into the WLAN by using these information. (1) SSID Spoofing Because SSID is shared between AP and clients, hackers can get SSID easily. This becomes a kind of method of attacking WLAN. Because AP broadcasts data to all clients, they can find AP name, channel, SSID and MAC address in these data. So Hackers can listen these data and get them easily. Hackers can attack WLAN by using SSID association. Netstumbler software attack WLAN by using this theory too. Sometimes the AP use default SSID value to communicate with the clients. Then hackers can get the SSID from the vendors more easily. (2) MAC Spoofing As mentioned before, MAC filtering is a kind of security mechanism of WLAN, but it is insecure. Hackers can attack WLAN by using this. MAC filtering provides security with the way only allowed valid MAC addresses get into the WLAN. These can be set in the AP. Some MAC addresses can be allowed to use the WLAN and others can’t be allowed to use the WLAN. But if a hacker get these messages, he can change his MAC address to a valid MAC address to break into the WLAN. They can use some crack software to gain MAC addresses easily. (3) Authentication Spoofing of WEP If clients want to communicate with AP, they have to pass the WEP authentication. The process of WEP authentication as follow: AP sends a 128-byte random string to the client wishing to authenticate. The client then encrypts the message to the AP. If the message matches then the AP will allow the client to use the WLAN, otherwise refuse. In this process, hackers can acquire both the original plaintext and cipher messages at the same time. So they can create a fake authentication message that AP will authenticate a valid user. Sometimes hackers can acquire the WEP key from windows register, so the attacking will become more easily. Because the WEP key is shared between all communication stations. WEP algorithm implements on the basis of RSA’s RC4 encryption algorithm, but RC4 encryption algorithm has some weaknesses. So hackers can crack WEP key by using these weaknesses. We will discuss it in the next section. Ⅲ. THE ANALYZING OF WEP ALGORITHM Until now we have know that the security of WLAN is mostly depended on the security of WEP key. But as mentioned before, WEP uses RC4 encryption algorithm. We can crack WEP key by using RC4’s weaknesses. A. WEP Algorithm WEP encryption process as follow: The data frame is check summed (using the CRC-32) to obtain c(M), where M is the message. M and c(M) are concatenated to get the plain text P=(M, c(M)). RC4 key stream is generated by a function of the initialization vector IV and the secret key =RC4 (IV, K). The cipher text results from applying the XOR function to the plain text and the key stream. That is (M, c (M)) XOR RC4 (v, K). At last, cipher text and IV are transmitted in the forms of electromagnetic wave. By WEP symmetrically cryptographic characteristic, decryption process is the reverse of the encryption process by using the same WEP key. The receiver uses IV and WEP Key to generate the key stream. We use XOR key stream with cipher text to recover the plaintext P1. The P1 is then split into two parts as message M1 and check sum C1. c(M1) is then computed and compared with C1, if matches we receive it ,or refuse. B. The Weaknesses of WEP Algorithm (1) Invariance Weakness RC4 is a kind of stream key algorithm widely used. RC4 is composed of key schedule algorithm (KSA) and pseudo-random generation algorithm (PRGA). In KSA process the WEP key is changed to a state array s with hundreds of plus and swap operation. The process of PRGA generates a pseudo-random stream. This stream is used to encrypt the plaintext or decrypt the cipher text. Some researches indicate that the RC4 algorithm is vulnerable in the aspect that every 256 keys or less produce one weak key. This is called invariance weakness[4]. These weak keys will result in the pseudorandom have the specific and recognizant prefix. Their relativity with the key will become low. The data that are encrypted with these weak keys will become breakable. (2) IV Weakness There is another weakness is repeat-used IV, which is called IV weakness[4]. The input key of RC4 is composed of 24bytes IV and 40 bytes WEP key. The IV is used to guarantee that the same plaintext will never generate the same cipher text. But many wireless cards reset the IV to 0 each time a card is initialized, and increment the IV by 1 with each packet. Because of the invariance of WEP key the data will be encrypted with the same key stream. Yet in WLAN the IV is transmitted with plaintext that will be acquired easily. There is another situation of repeat-used IV. Because the length of IV is only 24 bytes, every 224 packets will generate one repeat IV. So we can probably finger out that how much time will generate one repeat IV. An AP sends 1500 byte packets at 11 Mbps, and the time is about 1500*8/(11*10^6)*2^24=18000 seconds, which is about 5hours. Hackers can get the plaintext by using these repeat IVs. If two cipher texts that are encrypted with the same key stream XOR each other, it will generate the result of two plaintexts’ XOR because of the function of XOR. If one plaintext is known, another plaintext that is encrypted with the same key stream will be acquired easily. So the function of RC4 encryption is avoided. Hackers can crack WEP key by using these repeat IVs. One special formatted IV can be constructed. In this 40
condition the first byte output of pseudo-random sequence includes the key information. By observing a lot of this type of bytes we can recover the key bytes totally. The conformation of these special IVs is: X=SB+3[1]
Page 1 and 2: Proceedings The Second Internationa
Page 3 and 4: Table of Contents Message from the
Page 5 and 6: Zuming Xiao, Zhan Guo, Bin Tan, and
Page 7 and 8: Message from the Symposium Chairs T
Page 9 and 10: Second International Symposium on N
Page 11 and 12: ISBN 978-952-5726-09-1 (Print) Proc
Page 13 and 14: model that can deal with time serie
Page 17 and 18: training for the Wushu competition
Page 21 and 22: information, called weak uncertain
Page 23 and 24: Student side Student side Student s
Page 27 and 28: If we define element of student as
Page 31 and 32: QoS, each frame data is divided int
Page 35 and 36: for Imaging Two and Three Phase Flo
Page 39 and 40: A. Profiling&following control algo
Page 41 and 42: Research and Realization about Conv
Page 43 and 44: PDF document structure is a tree st
Page 47 and 48: support 10 Mb / s. But ENC28J60 onl
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Page 55 and 56: According to maximum membership deg
Page 59 and 60: ubber according to the mass ratio o
Page 61 and 62: Ⅲ. AN IMPROVED DNA ALGORITHM FOR
Page 63 and 64: Ⅴ.CONCLUSION REMARKS DNA computer
Page 65 and 66: its first child q 1 on the left, th
Page 67 and 68: chains can greatly improve efficien
Page 69 and 70: II. RELATED WORK A. Mobile Service
Page 71 and 72: special services. SOAP is used to b
Page 73 and 74: detection methods of DDoS attacks m
Page 75 and 76: Step4 calculate the new subordinate
Page 77 and 78: Figure 1. An analysis of the partit
Page 81 and 82: The preceding three formulas can be
Page 85 and 86: And the decay speed of buffer seque
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Page 93 and 94: Ⅳ. EVALUATION OF BLENDED LEARNING
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each sample belongs to each categor
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ISBN 978-952-5726-09-1 (Print) Proc
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A. Data Preparing To generate our t
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ISBN 978-952-5726-09-1 (Print) Proc
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oth α and β . determination of Qu
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ISBN 978-952-5726-09-1 (Print) Proc
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Strong earthquake 0.1< M L
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ISBN 978-952-5726-09-1 (Print) Proc
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indirect causes, and the logical re
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egression. Granger causality test i
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B. Evaluation We have evaluated thi
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used as a source and neighboring ce
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Figure 3. Drainage networks generat
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Combinational logic unit failures i
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Tabal.1 Combinational fault logic t
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under the endorsement of both the m
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TABLE I. DESCRIPTION OF PROPOSITION
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Figure 2. The process of the invers
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Figure 9. (a)the original image.(b)
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ISBN 978-952-5726-09-1 (Print) Proc
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In order to reduce to the number of
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ISBN 978-952-5726-09-1 (Print) Proc
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that studying being going to be to
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Reference[10] analyzed the evolutio
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module, communication module, apper
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After the comprehensive performance
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system testing can be seen that the
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III. AUTONOMIC RESOURCE ALLOCATION
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The QoE i (T i ) is the ith user’
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ISBN 978-952-5726-09-1 (Print) Proc
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nodes will be formed one cluster, t
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ISBN 978-952-5726-09-1 (Print) Proc
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Where n is the number of data point
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ISBN 978-952-5726-09-1 (Print) Proc
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Keyboard event Application User mod
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ISBN 978-952-5726-09-1 (Print) Proc
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SQL Azure will eventually include a
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ISBN 978-952-5726-09-1 (Print) Proc
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The nodes in the suffix tree are dr
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[3] Y. Li, S. M. Chung, and J. D. H
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some drilling fluid produces hydrog
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"normalization", whose membership b
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and minimum structural elements in
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esults of the spatial transform par
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B. Research on protocol actions Com
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ACKNOWLEDGMENT This work is funded
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A. Problem Description In a small b
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[4] Huang, Hung, and J. Y. jen Hsu.
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Further by calculating, the followi
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TABLE II. THE CONCENTRATION BETWEEN
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private key that obtained by using
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ISBN 978-952-5726-09-1 (Print) Proc
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ontology, and the domain dictionary
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ISBN 978-952-5726-09-1 (Print) Proc
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Eq.4 is NP-hard and can be solved b
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ISBN 978-952-5726-09-1 (Print) Proc
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Where: G i is the selection field o
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If there is X j in a generation, wh
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Theorem 2.4([10]). Let L 1 and L 2
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The relation between the lattice im
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Figure 2. Example of single-step de
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evocation and the fourth group stor
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focused mainly on rule-based forms
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Ⅵ. CONCLUSION Figure 6. The Flask
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EDCF in comparison with DCF, has so
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B. Simulation results and analysis
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ISBN 978-952-5726-09-1 (Print) Proc
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in routing table. When search resou
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ISBN 978-952-5726-09-1 (Print) Proc
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others through the selective emotio
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such as weather information, techno
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the opening window, a related page
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1) Process context storage areas. I
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V. CONCLUSION In this thesis, sCPU-
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main types of horizontal search env
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Enterprise Portal security provides
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() t = [ S () t S () t ] T N S ,...
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[2] Kumaravel, N., and Kavitha, V.,
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output, so BP network has been wide
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input to the artificial neural netw
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(2) In a process (tokens from outsi
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The reduction process consists of t
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all eight normal vectors are identi
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is B object , and the number of emp
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xi, j y' = εα ( (1 + tanh( )) −
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Error 8000 7000 6000 5000 4000 3000
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Architecture (AMBA) a new bus archi
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In order to ensure the smooth proce
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ISBN 978-952-5726-09-1 (Print) Proc
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In this paper, we adopt two Sobel o
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ISBN 978-952-5726-09-1 (Print) Proc
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four layers.The far right of the gr
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ISBN 978-952-5726-09-1 (Print) Proc
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TABLE II. OPERATIONAL EMPLOYEE TABL
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A. Object-relational Type To audit
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to execution time. Also, DBA would
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Liping Chen .......................
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