Wednesday, 18 April 2018

EDWARD SNOWDEN

Global surveillance disclosures

The exact size of Snowden's disclosure is unknown, but Australian officials have estimated 15,000 or more Australian intelligence files and British officials estimate at least 58,000 British intelligence files NSA Director Keith Alexander initially estimated that Snowden had copied anywhere from 50,000 to 200,000 NSA documents Later estimates provided by U.S. officials were on the order of 1.7 million, a number that originally came from Department of Defense talking points. In July 2014, The Washington Post reported on a cache previously provided by Snowden from domestic NSA operations consisting of "roughly 160,000 intercepted e-mail and instant-message conversations, some of them hundreds of pages long, and 7,900 documents taken from more than 11,000 online accounts. A U.S. Defense Intelligence Agency report declassified in June 2015 said that Snowden took 900,000 Department of Defense files, more than he downloaded from the NSA.
In March 2014, Army General Martin Dempsey, Chairman of the Joint Chiefs of Staff, told the House Armed Services Committee, "The vast majority of the documents that Snowden exfiltrated from our highest levels of security ... had nothing to do with exposing government oversight of domestic activities. The vast majority of those were related to our military capabilities, operations, tactics, techniques and procedures. When asked in a May 2014 interview to quantify the number of documents Snowden stole, retired NSA director Keith Alexander said there was no accurate way of counting what he took, but Snowden may have downloaded more than a million documents.
According to Snowden, he did not indiscriminately turn over documents to journalists, stating that "I carefully evaluated every single document I disclosed to ensure that each was legitimately in the public interest. There are all sorts of documents that would have made a big impact that I didn't turn over and that "I have to screen everything before releasing it to journalists ... If I have time to go through this information, I would like to make it available to journalists in each country. Despite these measures, the improper redaction of a document by The New York Times resulted in the exposure of intelligence activity against al-Qaeda.[84]
In June 2014, the NSA's recently installed director, U.S. Navy Admiral Michael S. Rogers, stated that while some terrorist groups had altered their communications to avoid surveillance techniques revealed by Snowden, the damage done was not significant enough to conclude that "the sky is falling. Nevertheless, in February 2015, Rogers said that Snowden's disclosures had a material impact on the NSA's detection and evaluation of terrorist activities worldwide.
On 14 June 2015, UK's Sunday Times reported that Russian and Chinese intelligence services had decrypted more than 1 million classified files in the Snowden cache, forcing the UK's MI6 intelligence agency to move agents out of live operations in hostile countries. Sir David Omand, a former director of the UK's GCHQ intelligence gathering agency, described it as a huge strategic setback that was harming Britain, America, and their NATO allies. The Sunday Times said it was not clear whether Russia and China stole Snowden's data or whether Snowden voluntarily handed it over to remain at liberty in Hong Kong and Moscow. In April 2015 the Henry Jackson Society, a Britishneo conservative think tank, published a report claiming that Snowden's intelligence leaks negatively impacted Britain's ability to fight terrorism and organized crime. Gus Hosein, executive director of Privacy International, criticized the report for, in his opinion, presuming that the public became concerned about privacy only after Snowden's disclosures.

Sunday, 23 April 2017

DSP Application on One Dimension Signal

IEEE Paper Review: Implementation of a modem based on Quadrature Amplitude Modulation using TMS320C6201 DSP
Authors: N Dahnoun and D R Clewer
Publisher: IEEE
Published in: IEE Colloquium on DSP Chips in Real-Time Instrumentation and Display Systems
Location: Leicester, UK,
Date of Conference: 24 September 1997

Summary
Modems have traditionally been used to enable data communications via PSTN. This is severely band limited channel, requiring use of highly bandwidth efficient modulation schemes such as Quadrature Amplitude Modulation (QAM) combined with forward error correction and data compression in order to achieve bit rates up to 56 Kbps. The advances in DSP technology have recently enabled these bits rate to be achieved in commercial equipment at a reasonable cost. TMS320C6201 device boasts a maximum of 1600 MIPS at a clock speed of 200 MHz which is said to be more than a magnitude faster than any other fixed-point DSP. Cable modems allowing 36 Mbps transmission rates could be implemented using the same. Each module in transmitter as well as receiver was tested individually by writing a test program to read data in from a file, run the module and write the results on an output file. The data output were compared with expected output to judge failure and success of the DSP processor. To conclude, it was found that programming large functions in C on the DSP processor is both quick and easier than programming in assembler. 

Link: http://ieeexplore.ieee.org/document/659698/


Patent Review: Method for generating modern transmission signals with quadrature amplitude modulation.

Application Number: 06/136733 
Application Date: 04/27/1982 
Filling Date: 04/02/1980 
Inventors: Gockler, Heinz and Hofmeister, Hagen

Summary: 
The present invention relates to a method for generating modem transmission signals with quadrature amplitude modulation (QAM) in which scanned values of elementary bandpass signals are formed in digitally coded form, the elementary bandpass signals are weighted with coefficients depending on the information to be transmitted and the modem transmission signals are formed by superposition of the thus weighted elementary bandpass signals. It is therefore the object of the present invention to provide a method for generating modem transmission signals which operates with less calculating operations and thus enables the circuit to operate at a greater speed and with greater accuracy. The above object is accomplished according to one embodiment of the invention in that in a method for generating modem transmission signals with quadrature amplitude modulation (QAM). Another advantage of the invention is that in the case of m-ASK where m=2, 3, 4, . . .  the elementary bandpass signals are additionally weighted with factors corresponding to the amplitude stages characteristic for the information to be transmitted.

Link: http://www.freepatentsonline.com/4327439.html

 

Basic Operations on DSP Processor

The main aim of this experiment was to make us familiar with the DSP processors and to perform basic arithmetic and signal processing operations.
In this experiment basic convolution operation was performed on Texas Instruments C2000 TMS320F28335 DSP processor. The code was written on Code Composer studio which is used as a platform for implementing and debugging the codes. The advantage of using DSP processor is that, it is capable of handling large mathematical operations and also real time data can be processed with higher speed. For emulation XDS100v2 USB Emulator was selected. The output of the instructions was stored in the registers. In order to obtain the real time values of the register, the debugging functionality of the software was use.




Design of FIR filter using Frequency Sampling Method

Frequency sampling method is an alternative method to design FIR filter.

Frequency sampling method:
In this experiment various parameters such as passband attenuation, stop attenuation, passband frequency and stopband frequency and sampling frequency are passed as input. In this method the desired frequency response which is given as Hd(w) is sampled at w=2*pi*k/N where N is the length of the signal. The frequency sampled obtained are thus taken as DFT coefficients H[k].
FIR filter response is now obtained by taking Inverse Discrete Fourier Transform of H[k]. The results were verified by comparing the stopband and passband attenuation from the magnitude and phase spectrum which were plotted.

Wednesday, 12 April 2017

FIR filter Design using window Method

FIR filter Design using window Method

Depending upon the value of passband attenuation and stopband attenuation, appropriate window function was chosen from Hanning, Hamming, Blackman, Rectangular and Barlett.We have implemented the code in Scilab. In case of FIR filter the phase response of the filter varies linearly with the frequency thus the output of the filter is delayed version of the input by some constant and there is no distortion in the output. 

Design of Chebyshev Filter

Design of Chebyshev Filter.
The design procedure of chebyshev filter is very smiliar to that of Butterwoth Filter. In this experiment we implemented the Chebyshev Filter using BLT method. The parameters which were earlier used for design of butterworth filter are used for chebyshev filter. The magnitude response of chebyshev filter has ripple in passband depending upon the order of the filter and has monotonic response in stopband.

Design of Butterworth filter

Design of Butterworth Filter
This was the first experiment from which we started implementing the code in Scilab. Scilab is a software which is very similar to that of MATLAB. The biggest advantage of using Scilab software is that, it is an open source software. Initially we downloaded the Scilab software in all the PC's.
In this experiment various parameters such as passband attentuation, stopband attenuation, stopband frequency and passband frequency were passed as inputs and the code was implemented in such a way that it would calculate the order of the filter as well as the transfer function of the filter in Z domain. The steepness of the curve depends upon the order of the filter. Butterworth filter has monotonic passband as well as monotonic stopband.