Blockchain-based end-to-end encryption for Matrix instant messaging

Privacy and security in online communication is an important topic today, especially in the context of instant messaging. A lot of progress has been made in recent years to ensure that conversations are secure against attacks by third parties, but privacy from the service provider itself remains difficult. There are a number of solutions offering end-to-end encryption, but most of them rely on a centralized server, proprietary clients, or both. In order to have fully secure instant messaging conversations, a decentralized and end-to-end encrypted communication protocol is needed. This means there is no single point of control, and each message is encryped directly on the user's device such that only the recipient can decrypt it. This work proposes an end-to-end encryption system for the Matrix protocol based on blockchain technology. Matrix is a decentralized protocol and network for real-time communication that is currently mostly used for instant messaging. This protocol was selected because of its versatility and extensibility. Using the Secret Store feature in OpenEthereum, the proposed system encrypts data using keys stored on the Ethereum blockchain. Access control to the keys is also handled by the Secret Store via a smart contract. The proposed encryption system has multiple advantages over alternative schemes: The underlying blockchain technology reduces the risk of data loss because of its decentralized and distributed nature. Thanks to the use of smart contracts this system also allows for the creation of an advanced access control system to decryption keys. In order to test and analyze the proposed design, a reference implementation was created in the form of a library. This library can be used for future research, but also as a building block for different applications to easily implement end-to-end encryption based on blockchain technology

An optimized pseudorandom generator using packed matrices

Most cryptographic services and information security protocols require a dependable source of random data; pseudorandom generators are convenient and efficient for this application working as one of the basic foundation blocks on which to build the required security infrastructure. We propose a modification of a previously published matricial pseudorandom generator that significantly improves performance and security by using word packed matrices and modifying key scheduling and bit extraction schemes. The resulting generator is then successfully compared to world class standards.This research was partially supported by the Spanish grant GV06/018

Secure Messaging with in-app user defined schemes

Cryptography has been the culmination of human trials and mistrials in an attempt to keep information safe from unintended access. We have learned from our mistakes in the past, and today with the help of both academician and software developers, we have robust cryptographic technologies. Cryptography however, is a race between increasing processing power of modern machines and the complexity of cryptographic systems. With quantum computing on the horizon, our present cryptographic systems seem to fall behind in this race. There is a need to catalyze research in the field. Here, an application is proposed, which empowers users to write their own cryptographic schemes. It hopes to create a platform where people can share their cryptographic schemes and have an application that can help them share information securely. The author hopes, that an application which sources cryptographic schemes from users, would help catalyze research in the field. An application where the security implementation is dependent on the whim of the user could prove a hard target for attack. The thesis starts with a preliminary study of the Android platform. The thesis then analyzes im- plementations of a few secure messaging applications and then delves into details of NFC. Using the background information accumulated during the course of this study, the authors attempt to formulate a sound implementation of a messaging application. The thesis is also accompanied with a proof-of-concept Android application that checks the viability of concepts discussed herein

Deniable Key Exchanges for Secure Messaging

Despite our increasing reliance on digital communication, much of our online discourse lacks any security or privacy protections. Almost no email messages sent today provide end-to-end security, despite privacy-enhancing technologies being available for decades. Recent revelations by Edward Snowden of government surveillance have highlighted this disconnect between the importance of our digital communications and the lack of available secure messaging tools. In response to increased public awareness and demand, the market has recently been flooded with new applications claiming to provide security and privacy guarantees. Unfortunately, the urgency with which these tools are being developed and marketed has led to inferior or insecure products, grandiose claims of unobtainable features, and widespread confusion about which schemes can be trusted. Meanwhile, there remains disagreement in the academic community over the definitions and desirability of secure messaging features. This incoherent vision is due in part to the lack of a broad perspective of the literature. One of the most contested properties is deniability—the plausible assertion that a user did not send a message or participate in a conversation. There are several subtly different definitions of deniability in the literature, and no available secure messaging scheme meets all definitions simultaneously. Deniable authenticated key exchanges (DAKEs), the primary cryptographic tool responsible for deniability in a secure messaging scheme, are also often unsuitable for use in emerging applications such as smartphone communications due to unreasonable resource or network requirements. In this thesis, we provide a guide for a practitioner seeking to implement deniable secure messaging systems. We examine dozens of existing secure messaging protocols, both proposed and implemented, and find that they achieve mixed results in terms of security. This systematization of knowledge serves as a resource for understanding the current state-of-the-art approaches. We survey formalizations of deniability in the secure messaging context, as well as the properties of existing DAKEs. We construct several new practical DAKEs with the intention of providing deniability in modern secure messaging environments. Notably, we introduce Spawn, the first non-interactive DAKE that offers forward secrecy and achieves deniability against both offline and online judges; Spawn can be used to improve the deniability properties of the popular TextSecure secure messaging application. We prove the security of our new constructions in the generalized universal composability (GUC) framework. To demonstrate the practicality of our protocols, we develop and compare open-source instantiations that remain secure without random oracles

Extending AES with DH Key-Exchange to Enhance VoIP Encryption in Mobile Networks

Recently,the evolution and progress have become significant in the field of information technology and mobile technology, especially inSmartphone applications that are currently widely spreading. Due to the huge developments in mobile and smartphone technologies in recent years, more attention is given to voice data transmission such as VoIP (Voice overIP) technologies– e.g. (WhatsApp, Skype, and Face Book Messenger). When using VoIP services over smartphones, there are always security and privacy concerns like the eavesdropping of calls between the communicating parties. Therefore, there is a pressing need to address these risks by enhancing the security level and encryption methods. In this work, we use scheme to encrypt VoIP channels using (128, 192 & 256-bit) enhanced encryption based on the Advanced Encryption Standard (AES) algorithm, by extending it with the well-known Diffie-Hellman (DH) key exchange method. We have performed a series of real tests on the enhanced (AES-DH) algorithm and compared its performance with the generic AES algorithm. The results have shown that we can get a significant increase in the encryption strength at a very small overhead between 4% and 7% of execution timebetween AES and AEScombine withDH for all scenario which was incurred by added time of encryption and decryption. Our approach uses high security and speed and reduces the voice delay.In dealing with sound transfer process via the internet, we use the SIP server to authenticate the communication process between the two parties. The implementation is done on a mobile device (Which is operated by (Android) system) because it has recently been widely used among different people around the world.اصبحت الثورة والتطور كبيرة حديثاً في حقول تكنولوجيا االتصاالت واليواتف النقالة، وخصوصا في تطبيقات اليواتف الذكية التي تنتشر حاليا بشكل واسع. وتم اعطاء المزيد من االىتمام لنقل البيانات الصوتية مثل تكنولوجيا االتصال عبر بروتكول االنترنت، عمى سبيل المثال: )الواتساب، السكايب، الفيس بوك، والماسنجر(. ويعزى ذلك لمتطور الكبير في تكنولوجيا اليواتف النقالة والذكية في السنوات االخيرة. عند استخدام خدمات االتصال عبر بروتكول االنترنت VoIP ،ىناك مخاوف دائمة حول الحماية والخصوصية كالتجسس عمى المكالمات بين جيات االتصال. ولذلك ىنالك حاجة ماسة لمعالجة ىذه المخاطر عن طريق تحسين مستوى الحماية وطرق التشفير. في ىذا العمل، نستخدم/ نجمع بين اثنتين من الخوارزميات لتشفير قنوات االتصال عبر بروتوكول االنترنت )128 ، 192 ،و 256 بت( عبر خوارزمية AESوتمديدىا عبر طريقة تبادل ديفي ىيممان الرئيسية المعروفة. وقمنا باداء العديد من التجارب الحقيقية عمى DH-AES ، وقمنا بمقارنة ادائيا مع اداء خوارزمية معيار التشفير المتقدم العامة. اظيرت النتائج انو بامكاننا الحصول عمى زيادة كبيرة في قوة التشفير بنسبة صغيرة جدا بين 4 %و7 %من وقت التنفيذ بين AESو DH/AES لجميع السيناريو والتي تم تكبدىا من قبل الوقت المضاف لمتشفير وفك التشفير. يستخدم نيجنا درجة عالية من الحماية والسرعة ويقمل من تأخير الصوت، ونستخدم في التعامل مع عممية نقل الصوت عبر االنترنت Server SIPلتوثيق عممية االتصال بين الجيتين. وتم التنفيذ عمى ىاتف نقال يعمل عمى نظام اندرويد؛ النو استخدم بشكل واسع مؤخرا بين مختمف الناس حول العالم