Integrity-protecting block cipher modes - Untangling a tangled web

This paper re-examines the security of three related block cipher modes of operation designed toprovide authenticated encryption. These modes, known as PES-PCBC, IOBC and EPBC, were all proposed in the mid-1990s. However, analyses of security of the latter two modes were published more recently. In each case one or more papers describing security issues with the schemes were eventually published, although a flaw in one of these analyses (of EPBC) was subsequently discovered - this means that until now EPBC had no known major issues. This paper establishes that, despite this, all three schemes possess defects which should prevent their use - especially as there are a number of efficient alternative schemes possessing proofs of security

Analysing the IOBC Authenticated Encryption Mode

Abstract. The idea of combining a very simple form of added plaintext redundancy with a special mode of data encryption to provide data in-tegrity is an old one; however, despite its wide deployment in protocols such as Kerberos, it has largely been superseded by provably secure au-thenticated encryption techniques. In this paper we cryptanalyse a block cipher mode of operation called IOBC, possibly the only remaining en-cryption mode designed for such use that has not previously been ana-lyzed. We show that IOBC is subject to known-plaintext-based forgery attacks with a complexity of around 2n=3, where n is the block cipher block length.

Symmetric Encryption Algorithms: Review and Evaluation Study

The increased exchange of data over the Internet in the past two decades has brought data security and confidentiality to the fore front. Information security can be achieved by implementing encryption and decryption algorithms to ensure data remains secure and confidential, especially when transmitted over an insecure communication channel. Encryption is the method of coding information to prevent unauthorized access and ensure data integrity and confidentiality, whereas the reverse process is known as decryption. All encryption algorithms aim to secure data, however, their performance varies according to several factors such as file size, type, complexity, and platform used. Furthermore, while some encryption algorithms outperform others, they have been proven to be vulnerable against certain attacks. In this paper, we present a general overview of common encryption algorithms   and explain their inner workings. Additionally, we select ten different symmetric encryption algorithms and conduct a simulation in Java to test their performance. The algorithms we compare are: AES, BLOWFISH, RC2, RC4, RC6, DES, DESede, SEED, XTEA, and IDEA. We present the results of our simulation in terms of encryption speed, throughput, and CPU utilization rate for various file sizes ranging from 1MB to 1GB. We further analyze our results for all measures that have been tested, taking into account the level of security they provide

Analysis and Design Security Primitives Based on Chaotic Systems for eCommerce

Security is considered the most important requirement for the success of electronic commerce, which is built based on the security of hash functions, encryption algorithms and pseudorandom number generators. Chaotic systems and security algorithms have similar properties including sensitivity to any change or changes in the initial parameters, unpredictability, deterministic nature and random-like behaviour. Several security algorithms based on chaotic systems have been proposed; unfortunately some of them were found to be insecure and/or slow. In view of this, designing new secure and fast security algorithms based on chaotic systems which guarantee integrity, authentication and confidentiality is essential for electronic commerce development. In this thesis, we comprehensively explore the analysis and design of security primitives based on chaotic systems for electronic commerce: hash functions, encryption algorithms and pseudorandom number generators. Novel hash functions, encryption algorithms and pseudorandom number generators based on chaotic systems for electronic commerce are proposed. The securities of the proposed algorithms are analyzed based on some well-know statistical tests in this filed. In addition, a new one-dimensional triangle-chaotic map (TCM) with perfect chaotic behaviour is presented. We have compared the proposed chaos-based hash functions, block cipher and pseudorandom number generator with well-know algorithms. The comparison results show that the proposed algorithms are better than some other existing algorithms. Several analyses and computer simulations are performed on the proposed algorithms to verify their characteristics, confirming that these proposed algorithms satisfy the characteristics and conditions of security algorithms. The proposed algorithms in this thesis are high-potential for adoption in e-commerce applications and protocols

Implementing and Evaluating Nonsingular Matrices Generators for the Hill Cipher

A Cifra de Hill (Hill Cipher) é um exemplo clássico de um sistema criptográfico com propriedades muito interessantes, nomeadamente a implementação dos conceitos de confusão e difusão apresentados por Shannon como propriedades essenciais para as cifras; no entanto, a sua forma básica é vulnerável a Known Plaintext Attacks (KPAs). [...]Hill Cipher is a classical example of a cryptosystem with interesting properties, namely that it implements the diffusion and confusion concepts coined by Shannon as essential properties for ciphers; nonetheless, its basic form is vulnerable to KPAs. [...

Breaking Into the KeyStore: A Practical Forgery Attack Against Android KeyStore

We analyze the security of Android KeyStore, a system service whose purpose is to shield users credentials and cryptographic keys. The KeyStore protects the integrity and the confidentiality of keys by using a particular encryption scheme. Our main results are twofold. First, we formally prove that the used encryption scheme does not provide integrity, which means that an attacker is able to undetectably modify the stored keys. Second, we exploit this flaw to define a forgery attack breaching the security guaranteed by the KeyStore. In particular, our attack allows a malicious application to make mobile apps to unwittingly perform secure protocols using weak keys. The threat is concrete: the attacker goes undetected while compromising the security of users. Our findings highlight an important fact: intuition often goes wrong when security is concerned. Unfortunately, system designers still tend to choose cryptographic schemes not for their proved security but for their apparent simplicity. We show, once again, that this is not a good choice, since it usually results in severe consequences for the whole underlying system

Differential Power Analysis of the SKINNY Family of Block Ciphers

The SKINNY family of lightweight block ciphers is well-researched in terms of standard cryptanalysis, but little has been done in the field of power analysis attacks. By sequentially dividing and conquering, univariate Differential Power Analysis attacks are performed against SKINNY. As the resulting diffusion from MixColumns introduces redundancy in terms of leakage, we introduce an alternative placement scheme for the tweak material in the related-tweakey setting to minimize leakage of the key material.Masteroppgave i informatikkINF399MAMN-INFMAMN-PRO

Ongoing Research Areas in Symmetric Cryptography

This report is a deliverable for the ECRYPT European network of excellence in cryptology. It gives a brief summary of some of the research trends in symmetric cryptography at the time of writing. The following aspects of symmetric cryptography are investigated in this report: • the status of work with regards to different types of symmetric algorithms, including block ciphers, stream ciphers, hash functions and MAC algorithms (Section 1); • the recently proposed algebraic attacks on symmetric primitives (Section 2); • the design criteria for symmetric ciphers (Section 3); • the provable properties of symmetric primitives (Section 4); • the major industrial needs in the area of symmetric cryptography (Section 5)

EasySMS: a protocol for end to end secure transmission of SMS

Nowadays, short message service (SMS) is being used in many daily life applications, including healthcare monitoring, mobile banking, mobile commerce, and so on. But when we send an SMS from one mobile phone to another, the information contained in the SMS transmit as plain text. Sometimes this information may be confidential like account numbers, passwords, license numbers, and so on, and it is a major drawback to send such information through SMS while the traditional SMS service does not provide encryption to the information before its transmission. In this paper, we propose an efficient and secure protocol called EasySMS, which provides end-to-end secure communication through SMS between end users. The working of the protocol is presented by considering two different scenarios. The analysis of the proposed protocol shows that this protocol is able to prevent various attacks, including SMS disclosure, over the air modification, replay attack, man-in-the-middle attack, and impersonation attack. The EasySMS protocol generates minimum communication and computation overheads as compared with existing SMSSec and PK-SIM protocols. On an average, the EasySMS protocol reduces 51% and 31% of the bandwidth consumption and reduces 62% and 45% of message exchanged during the authentication process in comparison to SMSSec and PK-SIM protocols respectively. Authors claim that EasySMS is the first protocol completely based on the symmetric key cryptography and retain original architecture of cellular network

Authenticated Encryption: How Reordering can Impact Performance

In this work, we look at authenticated encryption schemes from a new perspective. As opposed to focusing solely on the {\em ``security\u27\u27} implications of the different methods for constructing authenticated encryption schemes, we investigate the effect of the method used to construct an authenticated encryption scheme on the {\em ``performance\u27\u27} of the construction. We show that, as opposed to the current NIST standard, by performing the authentication operation before the encryption operation, the computational efficiency of the construction can be increased, without affecting the security of the overall construction. In fact, we show that the proposed construction is even more secure than standard authentication based on universal hashing in the sense that the hashing key is resilient to key recovery attacks