دانلود مقاله A comparative study of packet combining based error recovery schemes for wireless networks انتشار 2014

اختصاصی از اینو دیدی دانلود مقاله A comparative study of packet combining based error recovery schemes for wireless networks انتشار 2014 دانلود با لینک مستقیم و پر سرعت .

Int. J. Ad Hoc and Ubiquitous Computing, Vol. 16, No. 3, 2014

Sheng-Shih Wang*, Pei-Chun Lee, Kan-Yen Lin
and Tzu-Chang Yeh

Abstract: To provide reliable communications in wireless environments, two fundamental error
control mechanisms, automatic repeat request (ARQ) and forward error correction (FEC) are
proposed. However, the ARQ mechanism may suffer frequent retransmissions and the FEC
mechanism incurs bandwidth overhead. To reduce the number of retransmissions and support
efficient correction, previous studies have proposed numerous packet combining based error recovery
schemes. This study investigates the recovery performance of three packet combining based error
recovery schemes, including the extended ARQ (EARQ), the merge strategy in the simple packet
combining (SPaC-M), and the destination packet (DPC) schemes through the mathematical analysis
and simulations. Results present that the EARQ outperforms the SPaC-M and the DPC in recovery
speed in case of a large packet length and a high bit error rate. However, the EARQ is not suggested
if the space overhead is the major consideration.
Keywords: packet combining; error recovery; ARQ; automatic repeat request; FEC; forward error
correction.

دانلود مقاله Understanding security failures of two-factor authentication schemes for real-time applications in hierarchical wi

اختصاصی از اینو دیدی دانلود مقاله Understanding security failures of two-factor authentication schemes for real-time applications in hierarchical wireless sensor networks - انتشار 2014 دانلود با لینک مستقیم و پر سرعت .

• Contents lists available at ScienceDirect
  Ad Hoc Networks
• ADHOC 1019 No. of Pages 15, Model 3G
  27 March 2014
• Ding Wang^, ,Ping Wang

a b s t r a c t
Understanding security failures of cryptographic protocols is the key to both patching 
existing protocols and designing future schemes. In this work, we investigate two recent 
proposals in the area of smart-card-based password authentication for security-critical 
real-time data access applications in hierarchical wireless sensor networks (HWSN). Firstly, 
we analyze an efficient and DoS-resistant user authentication scheme introduced by Fan 
et al. in 2011. This protocol is the first attempt to address the problems of user authenti- 
cation in HWSN and only involves lightweight cryptographic primitives, such as one- 
way hash function and XOR operations, and thus it is claimed to be suitable for the 
resource-constrained HWSN environments. However, it actually has several security loop- 
holes being overlooked, and we show it is vulnerable to user anonymity violation attack, 
smart card security breach attack, sensor node capture attack and privileged insider attack, 
as well as its other practical pitfalls. Then, A.K. Das et al.’s protocol is scrutinized, and we 
point out that it cannot achieve the claimed security goals: (1) It is prone to smart card 
security breach attack; (2) it fails to withstand privileged insider attack; and (3) it suffers 
from the defect of server master key disclosure. Our cryptanalysis results discourage any 
practical use of these two schemes and reveal some subtleties and challenges in designing 
this type of schemes. Furthermore, using the above two foremost schemes as case studies, 
we take a first step towards investigating the underlying rationale of the identified security 
failures, putting forward three basic principles which we believe will be valuable to proto- 
col designers for advancing more robust two-factor authentication schemes for HWSN in 
the future.