The CS2 Block Cipher

In this paper we describe our new CS$^2$ block cipher which is an extension of the original CS-Cipher. Our new design inherits the efficiency of the original design while being upgraded to support a larger block size as well as use a slightly improved substitution box. We prove that our design is immune to differential and linear cryptanalysis as well as argue it resists several other known attacks

Re-Encryption Scheme for Providing Data Security in Clouds

Cloud computing is the trendy topic all over the world. With increase in popularity of cloud computing, more and more enterprises will outsource their sensitive data for sharing in a cloud. Cloud computing allows the users to share the data among the members of cloud. One of the issue in cloud computing is data security. Here the problem is whenever a user is revoked from cloud the data owners will send re-encryption command to cloud in order to re-encrypt the data so that the data is prevented from revoked users. In this paper, we propose a time-based re-encryption scheme using blowfish algorithm. This scheme allows the cloud to automatically re-encrypt the data based on the internal clock, users can access data within given time period, after time period get over user cannot access data, this scheme also prevents the revoked users from decrypting the data using their old decryption keys

Another Look at XCB

XCB is a tweakable enciphering scheme (TES) which was first proposed in 2004. The scheme was modified in 2007. We call these two versions of XCB as XCBv1 and XCBv2 respectively. XCBv2 was later proposed as a standard for encryption of sector oriented storage media in IEEE-std 1619.2 2010. There is no known proof of security for XCBv1 but the authors provided a concrete security bound for XCBv2 and a ``proof\u27\u27 for justifying the bound. In this paper we show that XCBv2 is not secure as a TES by showing an easy distinguishing attack on it. For XCBv2 to be secure, the message space should contain only messages whose lengths are multiples of the block length of the block cipher. For such restricted message spaces also, the bound that the authors claim is not justified. We show this by pointing out some errors in the proof. For XCBv2 on full block messages, we provide a new security analysis. The resulting bound that can be proved is much worse than what has been claimed by the authors. Further, we provide the first concrete security bound for XCBv1, which holds for all message lengths. In terms of known security bounds, both XCBv1 and XCBv2 are worse compared to existing alternative TES

Double Ciphertext Mode : A Proposal for Secure Backup

Security of data stored in bulk storage devices like the hard disk has gained a lot of importance in the current days. Among the variety of paradigms which are available for disk encryption, low level disk encryption is well accepted because of the high security guarantees it provides. In this paper we view the problem of disk encryption from a different direction. We explore the possibility of how one can maintain secure backups of the data, such that loss of a physical device will mean neither loss of the data nor the fact that the data gets revealed to the adversary. We propose an efficient solution to this problem through a new cryptographic scheme which we call as the double ciphertext mode (DCM). In this paper we describe the syntax of DCM, define security for it and give some efficient constructions. Moreover we argue regarding the suitability of DCM for the secure backup application and also explore other application areas where a DCM can be useful

Encrypted Communication between Two FITkits

Práce se zabývá problematikou šifrované komunikace mezi párem FITkitů. Výsledkem je implementace systému pro jednosměrný přenos krátkých textových zpráv pomocí rozhranní RS-232. Zprávy jsou šifrovány algoritmem AES-128 v módu CBC a jejich psaní a zobrazení zajišťují klávesnice a LCD displej FITkitu.This thesis is about encrypted communication between two FITkits. Thesis goal is implementation of system for short text message one-way transmission through RS-232 interface. Messages are encrypted by AES-128 algorithm working in CBC mode and their input and display are provided by keyboard and LCD display of FITkit device.

Verifying cryptographic software correctness with respect to reference implementations

This paper presents techniques developed to check program equivalences in the context of cryptographic software development, where specifications are typically reference implementations. The techniques allow for the integration of interactive proof techniques (required given the difficulty and generality of the results sought) in a verification infrastructure that is capable of discharging many verification conditions automatically. To this end, the difficult results in the verification process (to be proved interactively) are isolated as a set of lemmas. The fundamental notion of natural invariant is used to link the specification level and the interactive proof construction process.Fundação para a Ciência e a Tecnologia (FCT

Implementation of The Advanced Encryption Standard (AES) Algorithm for Digital Image Security

Nowadays, technological advances have made it increasingly easy to obtain information, especially image data (digital images). Digital image is an interesting thing to look for information. So that misuse of data can be done for personal or public interests. Misuse of data can be avoided by adding data security systems. Cryptography is the science of securing data. Cryptography can be done using the AES (Advanced Encryption Standard) algorithm, which is an algorithm that utilizes symmetric keys. Testing is done by entering the same key in the encryption and decryption process. Encryption is the process of encoding plaintext (original text) into ciphertext (text that has been encoded). While decryption is the process of recovering the plaintext from the ciphertext. Therefore, data security is an important thing to do. This study aims to find out how encryption and decryption on the AES algorithm can be used to secure digital data. The results of this study indicate that the encryption and decryption process on the AES algorithm was successfully carried out so that it can be used to secure data on digital images

Deductive verification of cryptographic software

We apply state-of-the art deductive verification tools to check security-relevant properties of cryptographic software, including safety, absence of error propagation, and correctness with respect to reference implementations. We also develop techniques to help us in our task, focusing on methods oriented towards increased levels of automation, in scenarios where there are clear obvious limits to such automation. These techniques allow us to integrate automatic proof tools with an interactive proof assistant, where the latter is used off-line to prove once-and-for-all fundamental lemmas about properties of programs. The techniques developed have independent interest for practical deductive verification in general.Fundação para a Ciência e a Tecnologia (FCT