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Optimization of Block Encryption Based Speech Coder Against Transmission Channel Noise

Thesis Info

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Author

Saeed, Manzar

Program

PhD

Institute

University of Engineering and Technology

City

Lahore

Province

Punjab

Country

Pakistan

Thesis Completing Year

2009

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/17

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726815792

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Compression of data has become a worldwide phenomenon during the past few decades for reason of achieving savings in band-width (BW) and hence makes it cost effective. The widespread practice of encryption of data has generated interest for many decades and it mainly aims at protection of data. Combining these two apparently contrary processes (in terms of BW) is quite challenging. Whereas the research on concurrent data compression and data protection (encryption) is still on, the methodology adopted by the author is unique and quite new. The most important aim of data compression technique is the need for curtailing the data storage and communication expenses. The source message (long) is converted to a codeword (small). The key objective of data encryption is to guard the integrity of data if it is intercepted by an eavesdropper. The plaintext is transformed in to ciphertext using an encryption key or keys. Combining the processes of compression and encryption together must be done in this order, that is, compression followed by encryption because all compression techniques heavily rely on the redundancies inherently part of a regular text or speech. The speech compression has been achieved using Lempel-Ziv 78 algorithm and a new algorithm for encryption/decryption, named ―The RandomOne, abbreviated as TR-1‖ is developed during this study and is thoroughly tested. The results obtained are quite encouraging. Firstly, contrary to the use of conventional methods the algorithm developed in this study does not use exclusive-OR (XOR) operation in Permutation (P) and Distribution (D) boxes for producing ciphertext from the plaintext. In this scheme pseudo random number (PRN) is used only to deceive the intruder by adding more confusion (meaning compared to the confusion due to the use of some tested algorithms used in this research). In fact only the sender of information and the intended recipient (not intruders) should be aware of the 44 bit positions filled by the PRN in a 128 word. The intended recipient discards these during deciphering process at the right time (these are disposed of before performing the inverse mapping in the P-Box). Secondly, protection against attacks is further ensured by using two supplementary keys, one for the P-Box, and another for the D-box. In addition the routine key-set of the N selected algorithms further enhances the security. In a small set-up, the distribution of key-set can be mutually agreed upon by the users; but in a large set-up, the distribution of these sets can be accomplished using standard key distribution techniques. Moreover, the proposed algorithm also differs from the other methods currently in use due to deployment of a ―sentinel marker”; which is not adopted by other algorithms and this proposal is purely the brain child of the author. The sentinel marker is part of the secret key which is pre-decided and predetermined by the sender and the intended recipient of the information. Twenty bits (out of a total of 128) are used for the sentinel marker which amounts to 2^20 = 1,048,576 possibilities combined with 2^44 = 17.6 trillion possibilities of the ciphertext produced by the PRN. The job for the cryptanalyst to break this cipher becomes formidable and a fool-proof security of data is ensured.
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معاشی ترقی میں تعلیم کا کردار

معاشی ترقی میں تعلیم کا کردار
نحمدہ ونصلی علی رسولہ الکریم امّا بعد فاعوذ بااللہ من الشیطن الرجیم
بسم اللہ الرحمن الرحیم
معزز سامعین اور میرے ہم مکتب ساتھیو!
آج مجھے جس موضوع پر لب کشائی کا موقع فراہم کیا گیا ہے وہ ہے:’’معاشی ترقی میں تعلیم کا کردار ‘‘
جنابِ صدر!
ہر شخص یہ چاہتا ہے کہ معاشرے میں میرا مقام بلند ہو جائے ، مجھے لوگ امیر انسان تصور کریں۔ میرے مشوروں پرعمل کیا جائے ، میری رائے کو اہمیت دی جائے ، میری شخصیت مسحور کن ہوں ،میری عادات متوازن ہوں ، میر ااٹھنا بیٹھنا معیاری ہو ، میری نشت و برخاست میں آن بان اور شان کی جھلک نمایاں ہو۔ میں طلسماتی شخصیت کا مالک ہوں۔
جنابِ صدر!
ان تمام اعزازات کے حصول کے لیے درعلم و حکمت پر دستک دینا پڑے گی ، اپنی معاشی حیثیت کو بحال کرنا ہوگا، کیونکہ جس کے گھر میں خوردونوش کا سامان نہ ہو، اس کی سوچ کے انداز تبدیل ہو جاتے ہیں وہ صرف یہ سوچتا ہے کہ رات کا کھانا کہاں سے آئے گا، بچوں کا پیٹ کس طرح پالا جائے گا، بچوں کو ڈھانپنے کے لیے کپڑے کہاں سے آئیں گے۔ اس کو اور کسی بات سے غرض نہیں۔
محترم صدر!
معاشی ترقی کے لیے تعلیم اہم کردار ادا کرتی ہے۔ تعلیم کے حصول سے نہ صرف انسان معاشی طور پر مضبوط ہو جاتا ہے بلکہ اس کی ترقی مثالی ہو جاتی ہے۔ جسمانی لوازمات کو پورا کرنے کے ساتھ ساتھ تعلیم اس کو روحانی تازگی اور تراوٹ بھی فراہم کرتی ہے اور نا جائز ذرائع سے معاشی آسودگی کا خواہش مندتحصیل علم کے بعد اپنی اسی خواہش کی تکمیل میں کوشاں رہتاہے۔
لاتی ہے گلستاں میں معیشت کی یہ بہار
تعلیم کی یہ جستجو ضائع نہیں جاتی
جنابِ...

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Pulsed Laser Deposition and Characterization of Epitaxial Multielement Oxide Thin Films

ZnO is a compound semiconductor from II-VI family which has been studied for more than fifty years because of versatile properties like wide direct band gap (3.37 eV), high optical transmittance in visible region (400-800 nm), high exciton binding energy (60 meV) and good electrical conductivity (~10-4 Ω-1.cm-1). Owing to these interesting properties, ZnO is a promising material for applications in different fields like optoelectronics for UV or blue LED’s, laser diodes, in optics as optical windows, anti-reflection coatings and in electronics for thin film transistors. ZnO is n-type semiconductor because of native defects, therefore, less solubility of acceptor impurities in ZnO and deep acceptor levels generated by p-type impurities like nitrogen and lithium, which increases the work function is reported as a reason behind unstable p-type conductivity of ZnO. Besides, a defect free epitaxial growth in form of thin films is also an important issue regarding use of ZnO in device fabrication, specifically LED’s and laser diodes. These issues provided basic initiative of this research project. Co-doping of ZnO with an acceptordonor impurity or acceptor-acceptor impurity can be effective for resolving conductivity-related issues. We have chosen rare-earths as donor impurity and group-I elements as acceptor impurity in ZnO to observe the p-type character whereas the epitaxial relationships are studied by depositing films on two single crystal substrates i.e. silicon and strontium titanate (STO). Apart from material being deposited, the thin film deposition process itself plays a critical role for determining the physical properties of as-deposited films. Pulsed laser deposition is selected in this project to deposit undoped and doped ZnO thin films on different substrates i.e. borosilicate glass, silicon and STO because of its uniqueness and variety of available parameters significantly affecting thin film characteristics. Laser pulses in two different time regimes: long pulse ~ nanoseconds and ultrashort pulse ~ femtoseconds are used for crystalline and nanocrystalline thin films respectively. Owing to scarcity of available literature on ultrashort laser deposition of ZnO, important PLD parameters for femto-pld are optimized using Ti: sapphire laser (wavelength = 800 nm, pulse repetition rate =1 kHz and pulse length = 100 femtoseconds). Three series of experiments are performed to deposit undoped ZnO thin films on borosilicate glass substrates varying like targetsubstrate distance, laser pulse energy, substrate temperature and deposition time. Highly c-axis iii oriented nanocrystalline ZnO thin films showing optical transmittance > 90% are obtained using these PLD conditions: dT-S =80 mm, El =180 μJ, PO2 =1 mTorr and TS = 100 °C. Three sets of rare-earth doped ZnO thin films are prepared. Set-I is deposited using 0, 2, 3, 4 and 5 wt.% yttrium doped ZnO (YZO) on (0 0 4) silicon substrates using nano-PLD. Microstructural analysis (XRD and Raman spectroscopy) shows films prefer c-axis growth under high interfacial stress. Very small amount of yttrium is doped at lattice sites and phase segregation is observed at higher concentrations. SE analysis revealed light absorption at lower wavelengths ≤ 370 nm and light transmission at higher wavelengths ≥ 400 nm. Set-II and set-III comprise yttrium and samarium doped ZnO respectively, deposited on glass employing optimized femto-PLD. Microstructural analysis (XRD and AFM) of both sets confirm nanocrystalline growth of films, supporting phase segregation at low (1 wt.%) and compound phase growth at high (10 wt.%) doping concentrations. Hetero-epitaxial Ag-Dy: ZnO (ADZO) and Li-Gd: ZnO (LGZO) thin films are deposited on (1 0 0) STO substrates employing optimized femto-PLD and nano-PLD respectively. Microstructural analysis indicates complete incorporation of silver atoms at lattice sites of zinc. Structural and optical analysis of LGZO thin films demonstrates significant modification in crystallinity and optical transmittance which indicates defect states lying within the energy gap of ZnO.It is concluded from rare-earth co-doped with Group-I element in ZnO leads to variety of defect generation caused by presence of metal oxides in their crystalline or non-crystalline phase and compound phases. Defects created by high concentration of rare-earth can increase the solubility limit of Group-I elements like silver and lithium, in ZnO. These dopants are capable of making acceptor levels in energy gap along with high (> 80%) optical transmittance. Heteroepitaxial growth of ZnO on (1 0 0) STO can be improved by co-doping ZnO with Ag and Dy.