Biblio
The challenge of maintaining confidentiality of stored and processed data in a remote database or cloud is quite urgent. Using homomorphic encryption may solve the problem, because it allows to compute some functions over encrypted data without preliminary deciphering of data. Fully homomorphic encryption schemes have a number of limitations such as accumulation of noise and increase of ciphertext extension during performing operations, the range of operations is limited. Nowadays a lot of homomorphic encryption schemes and their modifications have been investigated, so more than 25 reports on homomorphic encryption schemes have already been published on Cryptology ePrint Archive for 2016. We propose an overview of current Fully Homomorphic Encryption Schemes and analyze specific operations for databases which homomorphic cryptosystems allow to perform. We also investigate the possibility of sorting over encrypted data and present our approach to compare data encrypted by Multi-bit FHE scheme.
Many innovations in the field of cryptography have been made in recent decades, ensuring the confidentiality of the message's content. However, sometimes it's not enough to secure the message, and communicating parties need to hide the fact of the presence of any communication. This problem is solved by covert channels. A huge number of ideas and implementations of different types of covert channels was proposed ever since the covert channels were mentioned for the first time. The spread of the Internet and networking technologies was the reason for the use of network protocols for the invention of new covert communication methods and has led to the emergence of a new class of threats related to the data leakage via network covert channels. In recent years, web applications, such as web browsers, email clients and web messengers have become indispensable elements in business and everyday life. That's why ubiquitous HTTP messages are so useful as a covert information containers. The use of HTTP for the implementation of covert channels may increase the capacity of covert channels due to HTTP's flexibility and wide distribution as well. We propose a detailed analysis of all known HTTP covert channels and techniques of their detection and capacity limitation.