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

Folate, vitamin B6, vitamin B12, methionine and alcohol intake in relation to ovarian cancer risk
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1. Considering the Objective of the study and study design, was the method of dietary intake assessment valid and reliable? Why or why not?
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Wireless Sensor Network Protocols for Secure and Energy-Efficient Data
Sang-Eon Lee
, Sang-Ho Shin
, Geum-Dal Park
, Kee-Young Yoo
Dept. of Information Security, Kyungpook National University
Dept. of Computer Engineering, Kyungpook National University
Dept. of Electrical Engineering and Computer Science, Kyungpook National University
s4ng30n, shshin80, machunru2
Sensor networks are expected to be used at anywhere in
the near future and recently their security problems have
been rising. Due to the limited computing power of senor
nodes, 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 the
data encryption. In this paper, therefore, we propose a
key establishment and a data encryption scheme for secure
and energy-efficient data transmission in wireless sensor
networks (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. Introduction
Wireless sensor networks (WSNs) have currently been
used for a variety of applications such as environment mon-
itoring, health monitoring, military applications, etc. [1] and
also WSNs are expected to be used at anywhere in the near
future. To support many kinds of applications based on sen-
sor networks, the consideration of security aspects is essen-
For the satisfaction of security aspects, it is better to
apply well-known asymmetric cryptography such as RSA
and Diffie-Hellman algorithms to key establishment and ad-
vanced symmetric cryptography such as AES or DES to
data 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 only
512 bytes RAM space for data, 8K instruction flash, and
Corresponding author: Kee-Young Yoo (Tel.: +82-53-950-5553; Fax:
4500 bytes of available code space. Because of their inher-
ited resource limitation, advanced cryptographic methods
cannot 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 for
the 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 each
sensor node is deployed on the fields. Their key distri-
butions are based on asymmetric cryptography approaches
which need much more energy consumption and computing
power [6, 7]. Although satisfaction of security is high, it is
too heavy to apply to sensor node.
The pre-key distribution scheme is also classified into
the use of one master key in all nodes or individual key be-
tween two parties. If every node use one master key, it is
very 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
A key negotiation scheme in SPINS [3] was proposed by
A. Perrig et al. and BROSK [11] was proposed by C. Lai
et al. that they belong to a pre-key distribution scheme but
after deployment, they establish a session key between two
parties. 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 sensor
nodes. Every session key is created and distributed through
the base station. The traffic on sensor nodes near the base
station is increased and as a result, the battery is rapidly
consumed. In BROSK, the sensor node who wants to estab-
7th Computer Information Systems and Industrial Management Applications
978-0-7695-3184-7/08 $25.00 © 2008 IEEE
DOI 10.1109/CISIM.2008.24
lish a session key broadcasts a negotiation message which is
encrypted by the master key to his one-hop-neighbors. Be-
cause of this broadcasting method, it has the efficiency of
communication. However, when sensor nodes a establish
session key, this method totally depends on the master key
and it cannot authenticate each other at every key establish-
ment due to using same master key, i.e. their ID is open
in WSNs and they use same master key. So they cannot be
distinguished from each other.
Second, considering encryption researches, Hasan et
al. [9] evaluated several cryptographic encryption algo-
rithms such as AES, TEA (Tiny encryption algorithm), DES
and Blowfish (a mini-version of Blowfish). Their studies re-
veal that AES and DES require at a lot of memory space for
lookup tables and that these encryption algorithms are be-
yond a sensor node’s capacity. In SPINS, a counter mode is
used to encrypt the message in which the compacted RC5 is
coded. RC5 requires many memories on its key expansion
steps 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 and
energy-efficient data transmission in WSNs be used. The
key establishment scheme is an advanced hybrid key estab-
lishment scheme which has not only the efficiency of using
a unique secret key but also the security of using a random
key of each pair nodes. The data encryption scheme which
is suitable for WSNs uses only exclusive-OR (
) opera-
tion, message authentication code (
), and time-spacing
key derivation function (
) 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 proposed
protocol is presented. Then, the proposed protocol is ana-
lyzed how efficient it can be and whether it can meet several
security requirements or not in Section 5. Finally, the paper
is concluded.
2. Security Requirements
In this section, the security requirements on sensor net-
works are described.
Confidentiality means that some secret
information 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 the
nodes which have the shared key should be able to
check the information. In this way, the confidential-
ity is satisfied.
Authentication confirms the partici-
pant’s identity, so it distinguishes the legal users from
any potential attackers in the cyber communication
network. In the case of sensor networks, the data
which was given and taken among each sensor node
need verification whether the data come from a trust-
ful sender. If not, it permits false data, and it causes
trouble in the behavior of the network. Therefore, mu-
tual authentication can protect this problem.
Let the information be safe without any unex-
pected change in insecure networks by protecting the
information. In order to guarantee the integrity, the
sensor should become aware of any quick change of
the data such as the insertion, deletion, and substitu-
tion by unauthorized third parties. Integrity should be
guaranteed in many fields of sensor application such
as pollution and healthcare monitoring because they
require the exact result.
It guarantees the freshness of the message.
It means that the message should follow the order of
the message, and do not reuse the information. For
the freshness, network protocol should redesign the
method to identify the duplicate packets, and to cast
the message in order to prevent any possible mix-up.
An attacker’s insecure information gathering can dis-
turb the freshness.
3. Assumptions and Notations
In this section, some essential assumptions and notations
are 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 length
and its length is not too long. For example, the data
size of TinyOS is 28 bytes as a default [13]. In this
paper, a 32-byte key length and data length are used.

The sensor nodes transmit information to BS when
some events have occurred.
Next, the notations used throughout this paper as follows
(Table 1) are defined.
4. The Proposed Protocols
In this section, we propose key establishment scheme
and a data encryption scheme for secure and energy-
efficient data transmission in WSNs.

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