Interval-based flow watermarking for tracing interactive traffic

Tracing interactive attack traffic that traverses stepping stones (i.e., intermediate hosts) is challenging, as the packet headers, lengths, and contents can all be changed by the stepping stones. The traffic timing (delays between packets) has therefore been studied as a means of tracing traffic. One such technique uses traffic timing as a side channel into which a watermark, or identifying tag, can be embedded to aid with tracing. The effectiveness of such techniques is greatly reduced when the packet count of the traffic is changed at the stepping stone. Such transformations may occur as a result of either active countermeasures (e.g. chaff packets, flow splitting) by an adversary attempting to defeat tracing, or by incidental repacketization of the traffic by network interfaces.This paper presents a new method of embedding a watermark in traffic timing, for purposes of tracing the traffic in the presence of flow splitting, chaff packets, timing perturbation, and repacketization. This method uses an invariant characteristic of two connection flows which are part of the same stepping stone chain, namely, the elapsed time of the flows. The duration of each flow is sliced into short fixed-length intervals. Packet timing is adjusted to manipulate the packet count in specific intervals (without adding or deleting any packets), for purposes of embedding the watermark. The method is self-synchronizing and does not require clock synchronization between the watermark encoder and decoder.A statistical analysis of the method, with no assumptions or limitations concerning the distribution of packet times, proves the effectiveness of the method given a sufficient number of packets, despite natural and/or deliberate repacketization and countermeasures by an adversary. The method has been implemented and tested on a large number of SSH traffic flows. The results demonstrate that 100% detection rates and very low false positive rates are achieved under conditions of multiple countermeasures, and using only a few hundred packets.     

Enhancement of the punch pin durability induced by the PVD coating in production process of the automotive inner pipe

This experimental studies were carried out in order to understand the effects of the PVD coating and the UNSM treatment of HSS55 (high speed steel 55) during the production of the automotive inner pipe by the plastic deformation of S45C. The field test and the SEM images revealed that the PVD coating is necessary in spite of the high compressive residual stresses which were formed at the head of a punch pin. Upon the application of the AlCrN coating with the UNSM treatment the productivity and reliability of a punch pin had improved more than about 2.6 times compared to that of the TiN coating without the UNSM treatment. It is likely that the improvement is caused by the decreased stress concentration factor by the ‘wrapped in oxides’ inside of an abrasion pit. The abrasion pits were mostly generated within range of 5% ∼ 50% of the diameter ratio from the end of a pin and reached the maximum value about 17% from the end of a pin.     

A study on the restoration method of friction, wear and fatigue performance of remanufactured crankshaft

Crankshaft translates reciprocating linear piston motion into rotation in internal combustion engine. So it receives complex combination of stresses. Therefore, crankshaft remanufacturing process is designed thoroughly with special attention to fatigue and tribological performance. Experimental study is carried out in order to show that UNSM (ultrasonic nanocrystal surface modification) technology which will be used as final surface treatment after 0.2 mm depth surface grinding, could restore original fatigue strength and tribological performance. Furthermore the feasibility steady to replace conventional overlay welding in crankshaft remanufacturing process by UNSM (ultrasonic nanocrystal surface modification) technology is carried out. Effects of UNSM technology are established through rotary bending test, rolling contact fatigue (RCF) test and wear simulation test. The test specimen used SCM435 material of crankshaft and commercial bush. The test result showed fatigue limit improved by 30% and RCF life increased by 40% for UNSM treated specimen. And friction coefficient decreased by 24% and wear amount decreased by 85%.     

Corrosion and wear characteristics of pulse-plated chromium deposits

Corrosion and wear characteristics of pulse-plated chromium deposits, obtained from a self-regulating highspeed (SRHS) bath have been studied as a function of pulse current parameters such as duty cycle, average current density and pulse period. The chromium deposits obtained at duty cycles of 100 (direct current) to 60% were composed of a hemispherical nodular growth with a body centred cubic (b c c) lattice while those obtained at 20% duty cycle were composed of a needle-like structure containing a mixture of b c c lattice and hexagonal hydride. Corrosion rate, wear loss of chromium deposits and occluded hydrogen content in the deposits decreased up to 60% duty cycle, and then increased with further decrease in duty cycle to 20%. A two-stage variation of corrosion and wear properties with decreasing duty cycle is discussed in terms of crack density and the crystal structure of chromium deposits.     

A new slideline/eroding algorithm for EPIC2

This paper describes a new slideline/eroding algorithm implemented into EPIC2 code (Johnson , 1986). It also presents some results of impact calculations which show that this new algorithm not only better resolved the interface between two impacting bodies, but also smoothed out the curvature of the slideline. This was all done without an undue increase of CPU (central processing unit) time.     

Relationship between hydrogen-assisted crack propagation rate and the corresponding crack path in AISI 4340 steel

In the present investigation, relationship between hydrogen-assisted (HA) crack propagation rate and the corresponding fracture mode in AISI 4340 steel has been elucidated with critical hydrogen concentration concept. Hydrogen assisted crack-propagation rate and the corresponding fracture surface morphology were determined from double cantilever beam (DCB) specimens as a function of hydrogen pressure and temperature. As hydrogen pressure decreased, threshold stress intensity factor necessary for the onset of hydrogen-assisted crack propagation increased and the stage II (plateau) crack-propagation rate decreased. The kinetics of stage II crack propagation indicated substantial difference, i.e., positive and negative responses in the two investigated low and high temperature regions, respectively. Fractographic analysis showed that increased amounts of the microvoid coalescence mode resulted in slower crack-propagation rates. The observed changes in crack-propagation rate and the corresponding fracture mode with hydrogen pressure and temperature are discussed in terms of critical stress or strain and critical hydrogen concentration concepts.