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Folate, vitamin B6, vitamin B12, methionine and alcohol intake in relation to ovarian cancer risk

Paper details:I want some one to answer this question in one pagethis the article : http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3288483/the question :Questions:1. Considering the Objective of the study and study design, was the method of dietary intake assessment valid and reliable? Why or why not?2. In your opinion, what is the most important outcome of this study? Discuss why you think this is so.3. The Authors discuss several strengths and limitations of their analysis. Are there any additional limitations not already mentioned? Of those limitations mentioned, are there any that severely impact the study quality?4. Using the Quality Criteria Checklist (handed out in class and posted in the Course Documents fodler, QCC), how would your rate the quality of this study (+, – or 0), and what is the major reason for your quality grade?Wireless Sensor Network Protocols for Secure and Energy-Efficient DataTransmissionSang-Eon Lee1, Sang-Ho Shin2, Geum-Dal Park3, Kee-Young Yoo2§1Dept. of Information Security, Kyungpook National University2Dept. of Computer Engineering, Kyungpook National University3Dept. of Electrical Engineering and Computer Science, Kyungpook National Universityfs4ng30n, shshin80, machunru2g@infosec.knu.ac.kr, yook@knu.ac.krAbstractSensor networks are expected to be used at anywhere inthe near future and recently their security problems havebeen rising. Due to the limited computing power of senornodes, it is impossible to use asymmetric cryptography ap-proaches for the session key establishment or to apply ad-vanced encryption method such as AES and DES for thedata encryption. In this paper, therefore, we propose akey establishment and a data encryption scheme for secureand energy-efficient data transmission in wireless sensornetworks (WSNs). The proposed schemes just treat sim-ple operations as a message authentication code (MAC),exclusive-OR (XOR) and time-spacing key derivation func-tion (TSDF). Additionally, the security of the proposed pro-tocols is analyzed.1. IntroductionWireless sensor networks (WSNs) have currently beenused for a variety of applications such as environment mon-itoring, health monitoring, military applications, etc. [1] andalso WSNs are expected to be used at anywhere in the nearfuture. To support many kinds of applications based on sen-sor networks, the consideration of security aspects is essen-tial.For the satisfaction of security aspects, it is better toapply well-known asymmetric cryptography such as RSAand Diffie-Hellman algorithms to key establishment and ad-vanced symmetric cryptography such as AES or DES todata encryption. However, sensor nodes have low comput-ing power, storage, bandwidth and energy [2]. SmartDust[3], for instance, consist of a 8-bit, 4MHz CPU with only512 bytes RAM space for data, 8K instruction flash, and§Corresponding author: Kee-Young Yoo (Tel.: +82-53-950-5553; Fax:+82-53-957-4846)4500 bytes of available code space. Because of their inher-ited resource limitation, advanced cryptographic methodscannot be applied to sensor nodes.Various key distribution researches [2, 4, 5, 6, 7] and en-cryption of messages researches [3, 8, 9] were proposed forthe satisfaction of security and energy-efficiency in WSNs.First, considering key distribution researches, key distribu-tion schemes are classified into post-key and pre-key distri-bution according to the distributed time. In post-key distri-bution schemes, each shared key is established after eachsensor node is deployed on the fields. Their key distri-butions are based on asymmetric cryptography approacheswhich need much more energy consumption and computingpower [6, 7]. Although satisfaction of security is high, it istoo heavy to apply to sensor node.The pre-key distribution scheme is also classified intothe use of one master key in all nodes or individual key be-tween two parties. If every node use one master key, it isvery efficient, but its security depends only on master key.So, the reveal of the master key brings a high degree of dan-ger to all nodes. The method of using individual key be-tween two parties is more secure than using one master key,but it has a key management problem in each sensor node.For instance, when a new node joins in a sensor network,its neighborhood also updates a new node’s individual key[10].A key negotiation scheme in SPINS [3] was proposed byA. Perrig et al. and BROSK [11] was proposed by C. Laiet al. that they belong to a pre-key distribution scheme butafter deployment, they establish a session key between twoparties. In SPINS protocol, for the establishment of a ses-sion key between two parties, a trustful base station (BS)creates a session key and it is distributed to the two sensornodes. Every session key is created and distributed throughthe base station. The traffic on sensor nodes near the basestation is increased and as a result, the battery is rapidlyconsumed. In BROSK, the sensor node who wants to estab-7th Computer Information Systems and Industrial Management Applications978-0-7695-3184-7/08 $25.00 © 2008 IEEEDOI 10.1109/CISIM.2008.24157lish a session key broadcasts a negotiation message which isencrypted by the master key to his one-hop-neighbors. Be-cause of this broadcasting method, it has the efficiency ofcommunication. However, when sensor nodes a establishsession key, this method totally depends on the master keyand it cannot authenticate each other at every key establish-ment due to using same master key, i.e. their ID is openin WSNs and they use same master key. So they cannot bedistinguished from each other.Second, considering encryption researches, Hasan etal. [9] evaluated several cryptographic encryption algo-rithms such as AES, TEA (Tiny encryption algorithm), DESand Blowfish (a mini-version of Blowfish). Their studies re-veal that AES and DES require at a lot of memory space forlookup tables and that these encryption algorithms are be-yond a sensor node’s capacity. In SPINS, a counter mode isused to encrypt the message in which the compacted RC5 iscoded. RC5 requires many memories on its key expansionsteps and uses extreme circular shifts [12].In this paper, therefore, it is proposed that a key es-tablishment and a data encryption scheme for secure andenergy-efficient data transmission in WSNs be used. Thekey establishment scheme is an advanced hybrid key estab-lishment scheme which has not only the efficiency of usinga unique secret key but also the security of using a randomkey of each pair nodes. The data encryption scheme whichis suitable for WSNs uses only exclusive-OR (XOR) opera-tion, message authentication code (MAC), and time-spacingkey derivation function (TSDF) for efficiency and security.This paper is organized as follows: In section 2, the se-curity requirements are described. In section 3, the assump-tions and notations are explained. In section 4, the proposedprotocol is presented. Then, the proposed protocol is ana-lyzed how efficient it can be and whether it can meet severalsecurity requirements or not in Section 5. Finally, the paperis concluded.2. Security RequirementsIn this section, the security requirements on sensor net-works are described.=ConfidentialityConfidentiality means that some secretinformation should be protected against any third par-ties who are not certified. In the case of key establish-ments, they exchange secret information among nodes.This information should be encrypted, and only thenodes which have the shared key should be able tocheck the information. In this way, the confidential-ity is satisfied.=AuthenticationAuthentication confirms the partici-pant’s identity, so it distinguishes the legal users fromany potential attackers in the cyber communicationnetwork. In the case of sensor networks, the datawhich was given and taken among each sensor nodeneed verification whether the data come from a trust-ful sender. If not, it permits false data, and it causestrouble in the behavior of the network. Therefore, mu-tual authentication can protect this problem.=IntegrityLet the information be safe without any unex-pected change in insecure networks by protecting theinformation. In order to guarantee the integrity, thesensor should become aware of any quick change ofthe data such as the insertion, deletion, and substitu-tion by unauthorized third parties. Integrity should beguaranteed in many fields of sensor application suchas pollution and healthcare monitoring because theyrequire the exact result.=FreshnessIt guarantees the freshness of the message.It means that the message should follow the order ofthe message, and do not reuse the information. Forthe freshness, network protocol should redesign themethod to identify the duplicate packets, and to castthe message in order to prevent any possible mix-up.An attacker’s insecure information gathering can dis-turb the freshness.3. Assumptions and NotationsIn this section, some essential assumptions and notationsare mentioned. First, system assumptions and network re-strictions are mentioned. It is assumed that–WSNs are open networks, i.e. adversaries can eaves-drop on messages in communications.–Each wireless sensor node has an opened ID and iden-tical master key which is saved before it is deployed.–The message of data transmission has the same lengthand its length is not too long. For example, the datasize of TinyOS is 28 bytes as a default [13]. In thispaper, a 32-byte key length and data length are used.–The sensor nodes transmit information to BS whensome events have occurred.Next, the notations used throughout this paper as follows(Table 1) are defined.4. The Proposed ProtocolsIn this section, we propose key establishment schemeand a data encryption scheme for secure and energy-efficient data transmission in WSNs.158


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