Cipher Operations Research Articles

Efficient data confidentiality scheme for 5G wireless NOMA communications

Non-Orthogonal Multiple Access (NOMA) has recently emerged as a promising multiple access technique for current and future mobile communication networks. Unlike conventional multiple access schemes, NOMA exploits the power domain to service a large number of users at different power levels, using the same time–frequency resources. However, this technology suffers from major security threats since users are able to decode the messages of other paired users utilizing the same resources. In this paper, we propose an efficient and lightweight cipher scheme for NOMA systems at the physical layer. Unlike previous schemes in the literature, the proposed solution combines cryptography and Physical Layer Security (PLS) to provide robust security at minimum cost by adopting a structure that requires a single round with a single operation. Moreover, it is generic in the sense that any simple cipher operation such as permutation, substitution, phase shuffling, or pseudo-random masking, can be utilized in order to secure the underlying NOMA frame symbols. Also, we propose a dynamic key derivation scheme that benefits from the dynamic properties of wireless channels. Simulation results and cryptanalysis show that the proposed solution achieves the desired security level and strikes a good balance between performance and security level.

Secure MIMO D2D communication based on a lightweight and robust PLS cipher scheme

The Multiple-Input Multiple-Output (MIMO) technology is one of the key enablers of the 5G system. This technology allows the concurrent transmission of data using multiple antennas, which increases the channel robustness, overall throughput and link capacity. The security of 5G systems is very critical and it has received serious attention from various research groups. To that end, physical layer security (PLS) has recently emerged as a promising candidate to enhance network security, and several PLS schemes have been proposed for MIMO systems. Most of these MIMO PLS solutions target data confidentiality, however, they suffer from a main limitation due to relying solely on the random parameters of the channel. To overcome this limitation, we propose a PLS cipher solution for D2D MIMO systems, which is based on the dynamic key structure and several other factors including a private key and a physical channel parameter. Both of these parameters are combined to produce a dynamic key, which is used to generate the cipher primitives that are used to encrypt or decrypt data frames. For every input frame, the cipher primitives are updated, and for each frame symbol, the selection cipher primitives are updated. The update process is designed to enhance the security level and to ensure the avalanche effect in a simple and lightweight manner. Consequently, the proposed technique achieves high immunity against existing attacks due to the dynamic property which complicates the attacker’s tasks. A high efficiency level is also attained since a single round with simple cipher operations are employed. The proposed scheme decreases the required latency, resources and overhead in comparison to security schemes at upper layers of the D2D MIMO communication system. Finally, we conducted several security and performance tests to evaluate the proposed solution and to prove its robustness and efficiency.

A New Method for Format Preserving Encryption in High-Data Rate Communications

In some encryption systems it is necessary to preserve the format and length of the encrypted data. This kind of encryption is called FPE (Format Preserving Encryption). Currently, only two AES (Advanced Encryption Standard) modes of operation recommended by the NIST (National Institute of Standards and Technology) are able to implement FPE algorithms, FF1 and FF3. These modes work in an electronic codebook fashion and can be configured to encrypt databases with an arbitrary format and length. However, there are no stream cipher proposals able to implement FPE encryption for high data rate information flows. The main novelty of this work is a new block cipher operation mode proposal to implement an FPE algorithm in a stream cipher fashion. It has been called CTR-MOD and it is based on a standard block cipher working in CTR (Counter) mode and a modulo operation. The confidentiality of this mode is analyzed in terms of its IND- CPA (Indistinguishability under Chosen Plaintext Attack) advantage of any adversary attacking it. Moreover, the encryption scheme has been implemented on an FPGA (Field Programmable Gate Array) and has been integrated in a Gigabit Ethernet interface to test an encrypted optical link with a real high data rate traffic flow.

Self-Synchronized Encryption for Physical Layer in Gigabit Ethernet Optical Links

In this work a new self-synchronized symmetric encryption solution for high speed communication systems necessary to preserve the format of the plaintext is proposed, developed and tested. This new encryption mechanism is based on the block cipher operation mode called PSCFB (Pipelined Statistical Cipher Feedback) and the modulo operation. The confidentiality of this mode is analyzed in terms of its IND-CPA (Indistinguishability under Chosen-Plaintext Attack) advantage, concluding that it can be considered secure in the same way as traditional modes are. The encryption system has been integrated in the physical layer of a 1000Base-X Gigabit Ethernet Interface, where the 8b/10b symbol flow is encrypted at line rate. Moreover, an implementation of the proposed system has been carried out in an FPGA (Field Programmable Gate Array) device. Finally, an encrypted optical link has been tested with real Ethernet frames, getting maximum throughput and protecting the data traffic from passive eavesdroppers.

A VLIW architecture stream cryptographic processor for information security

As an important branch of information security algorithms, the efficient and flexible implementation of stream ciphers is vital. Existing implementation methods, such as FPGA, GPP and ASIC, provide a good support, but they could not achieve a better tradeoff between high speed processing and high flexibility. ASIC has fast processing speed, but its flexibility is poor, GPP has high flexibility, but the processing speed is slow, FPGA has high flexibility and processing speed, but the resource utilization is very low. This paper studies a stream cryptographic processor which can efficiently and flexibly implement a variety of stream cipher algorithms. By analyzing the structure model, processing characteristics and storage characteristics of stream ciphers, a reconfigurable stream cryptographic processor with special instructions based on VLIW is presented, which has separate/cluster storage structure and is oriented to stream cipher operations. The proposed instruction structure can effectively support stream cipher processing with multiple data bit widths, parallelism among stream cipher processing with different data bit widths, and parallelism among branch control and stream cipher processing with high instruction level parallelism; the designed separate/clustered special bit registers and general register heaps, key register heaps can satisfy cryptographic requirements. So the proposed processor not only flexibly accomplishes the combination of multiple basic stream cipher operations to finish stream cipher algorithms. It has been implemented with 0.18μm CMOS technology, the test results show that the frequency can reach 200MHz, and power consumption is 310mw. Ten kinds of stream ciphers were realized in the processor. The key stream generation throughput of Grain-80, W7, MICKEY, ACHTERBAHN and Shrink algorithm is 100Mbps, 66.67Mbps, 66.67Mbps, 50 Mbps and 800Mbps, respectively. The test result shows that the processor presented can achieve good tradeoff between high performance and flexibility of stream ciphers.

A VLIW architecture stream cryptographic processor for information security

As an important branch of information security algorithms, the efficient and flexible implementation of stream ciphers is vital. Existing implementation methods, such as FPGA, GPP and ASIC, provide a good support, but they could not achieve a better tradeoff between high speed processing and high flexibility. ASIC has fast processing speed, but its flexibility is poor, GPP has high flexibility, but the processing speed is slow, FPGA has high flexibility and processing speed, but the resource utilization is very low. This paper studies a stream cryptographic processor which can efficiently and flexibly implement a variety of stream cipher algorithms. By analyzing the structure model, processing characteristics and storage characteristics of stream ciphers, a reconfigurable stream cryptographic processor with special instructions based on VLIW is presented, which has separate/cluster storage structure and is oriented to stream cipher operations. The proposed instruction structure can effectively support stream cipher processing with multiple data bit widths, parallelism among stream cipher processing with different data bit widths, and parallelism among branch control and stream cipher processing with high instruction level parallelism; the designed separate/clustered special bit registers and general register heaps, key register heaps can satisfy cryptographic requirements. So the proposed processor not only flexibly accomplishes the combination of multiple basic stream cipher operations to finish stream cipher algorithms. It has been implemented with 0.18μm CMOS technology, the test results show that the frequency can reach 200MHz, and power consumption is 310mw. Ten kinds of stream ciphers were realized in the processor. The key stream generation throughput of Grain-80, W7, MICKEY, ACHTERBAHN and Shrink algorithm is 100Mbps, 66.67Mbps, 66.67Mbps, 50 Mbps and 800Mbps, respectively. The test result shows that the processor presented can achieve good tradeoff between high performance and flexibility of stream ciphers.

Reconfigurable chaotic pseudo random number generator based on FPGA

This paper presents an FPGA Pseudo Random Number Generator (PRNG) that is based on the Lorenz and Lü chaotic systems. These two systems are used to generate four different 3D chaotic attractors. One attractor is generated from Lorenz while the other three attractors are generated from Lü. The output attractor of the proposed PRNG can be reconfigured during real time operation using an efficient hardwired shifting and multiplexing scheme. Furthermore, in order to exploit the proposed reconfiguration feature, the proposed PRNG has been embedded in an FPGA cascaded encryption processor that ciphers the input data from one up to four times successively. In each ciphering operation the PRNG is set to a new configuration and is initialized according to a part of the encryption key. The size of the encryption key can be varied according to the number of required ciphering operations. The proposed PRNG has been realized using VHDL, synthesized on Xilinx using the FPGA device XC5VLX50T, and analyzed using MATLAB and the NIST statistical suite. The proposed PRNG has utilized only 1.4% from the FPGA’s slices, achieved an operating frequency up to 78 MHz, and successfully passed all the NIST statistical tests.

Comparison of Cost of Protection against Differential Power Analysis of Selected Authenticated Ciphers

Authenticated ciphers, which combine the cryptographic services of confidentiality, integrity, and authentication into one algorithmic construct, can potentially provide improved security and efficiencies in the processing of sensitive data. However, they are vulnerable to side-channel attacks such as differential power analysis (DPA). Although the Test Vector Leakage Assessment (TVLA) methodology has been used to confirm improved resistance of block ciphers to DPA after application of countermeasures, extension of TVLA to authenticated ciphers is non-trivial, since authenticated ciphers have expanded input and output requirements, complex interfaces, and long test vectors which include protocol necessary to describe authenticated cipher operations. In this research, we upgrade the FOBOS test architecture with capability to perform TVLA on authenticated ciphers. We show that FPGA implementations of the CAESAR Round 3 candidates ACORN, Ascon, CLOC (with AES and TWINE primitives), SILC (with AES, PRESENT, and LED primitives), JAMBU (with AES and SIMON primitives), and Ketje Jr.; as well as AES-GCM, are vulnerable to 1st order DPA. We then use threshold implementations to protect the above cipher implementations against 1st order DPA, and verify the effectiveness of countermeasures using the TVLA methodology. Finally, we compare the unprotected and protected cipher implementations in terms of area, performance (maximum frequency and throughput), throughput-to-area (TP/A) ratio, power, and energy per bit (E/bit). Our results show that ACORN consumes the lowest number of resources, has the highest TP/A ratio, and is the most energy-efficient of all DPA-resistant implementations. However, Ketje Jr. has the highest throughput.

Efficient Detection for Malicious and Random Errors in Additive Encrypted Computation

Although data confidentiality is the primary security objective in additive encrypted computation applications, such as the aggregation of encrypted votes in electronic elections, ensuring the trustworthiness of data is equally important. And yet, integrity protections are generally orthogonal to additive homomorphic encryption, which enables efficient encrypted computation, due to the inherent malleability of homomorphic ciphertexts. Since additive homomorphic schemes are founded on modular arithmetic, our framework extends residue numbering to support fast modular reductions and homomorphic syndromes for detecting random errors inside homomorphic ALUs and data memories. In addition, our methodology detects malicious modifications of memory data, using keyed syndromes and block cipher-based integrity trees, which allow preserving the homomorphism of ALU operations, while enforcing non-malleability of memory data. Compared to traditional memory integrity protections, our tree-based syndrome generation and updating is parallelizable for increased efficiency, while requiring a small Trusted Computing Base for secret key storage and block cipher operations. Our evaluation shows more than 99.999 percent detection rate for random ALUs errors, as well as 100 percent detection rate of single bit-flips and clustered multiple bit upsets, for a runtime overhead between 1.2 and 5.5 percent, and a small area penalty.

Two Efficient Fault-Based Attacks on CLOC and SILC

CLOC and SILC are two block cipher-based authenticated encryption schemes, submitted to the CAESAR competition, that aims to use low area buffer and handle short input efficiently. The designers of CLOC and SILC claimed $\frac {n}{2}$ -bit integrity security against nonce-reusing adversaries, where n is the blockcipher state size in bits. In this paper, we present single fault-based almost universal forgeries on both CLOC and SILC with only one single bit fault at a fixed position of a specific blockcipher input. In the case of CLOC, the forgery can be done for almost any nonce, associated data and message triplet, except some nominal restrictions on associated data. In the case of SILC, the forgery can be done for almost any associated data and message, except some nominal restrictions on associated data along with a fixed nonce. Both the attacks on CLOC and SILC require several nonce-misusing encryption queries This attack is independent of the underlying block cipher and works on the encryption mode. In this paper, we also validate the proposed fault-based forgery methodology by performing actual fault attacks by electromagnetic pulse injection which shows practicality of the proposed forgery procedure. Next, we provide updated constructions that can resist the fault-based forgery on the mode assuming the underlying block cipher is fault resistant. Finally, we show that, if the underlying block cipher is not fault resistant, then for both CLOC and SILC, the key recovery can be done by injecting fault into the block cipher operations. We have considered the example with AES as the underlying block cipher. We would like to note that our attacks do not violate the designers’ claims as our attacks require fault. However, it shows some vulnerability of the schemes when fault is feasible.

A Stream Cipher based on Spatiotemporal Chaos and True Random Synchronization

ABSTRACTStream ciphers require the use of initialization vectors (IVs) to ensure that the same secret key produces different keystreams. It also synchronizes communication between two parties. However, there are many cryptanalytic attacks that exploit weaknesses in the IV setup of stream ciphers. In an effort to solve this problem, we introduce a chaos-based stream cipher that utilizes a new mode of synchronization called true random synchronization (TRSync). The stream cipher is designed based on spatiotemporal chaos while taking advantage of TRSync to resist various statistical attacks. The stream cipher operations also include data-dependent rotations and chaotic perturbation. As chaotic functions are inherently slow due to floating point operations, we utilize fixed point representation for higher efficiency. TRSync includes a true random number sequence (TRNS) into the synchronization process alongside the public IV. The IV is masked by the TRNS before being used to setup the cipher. Therefore, the cipher's internal state cannot be manipulated by an attacker and constantly changes even if the secret key-IV pairs are constant. TRSync can also be used to secure other stream ciphers with IVs as described in this paper. The security of the proposed chaotic cipher is thoroughly analyzed in terms of randomness, periodicity, entropy, balance, correlation, and complexity.

A Novel Energy Efficient Key Distribution Scheme for Mobile WiMAX Networks

In Mobile WiMAX, a Base Station (BS) delivers security keys to Mobile Stations (MSs) through a key distribution scheme to guarantee security and access control. The MSs need to perform ciphering operations to access the keys upon rekeying process. In this way, the MSs consume energy to receive and decrypt the keys for further communication with a BS, while the BS consumes energy to encrypt and transmit the keys. In current key distribution schemes, any member join or leave event results in a key updating, and the duration of the MSs stay in the cell is not important, but on average low speed MSs tend to stay longer in the cell, while fast MSs will leave the cell faster. This paper proposes an Efficient Key Distribution scheme to decrease the number of exchanged keys which results in minimizing energy consumption of the network by grouping the MSs into the different subgroups based on their speeds using complete binary tree. Analysis shows that the proposed scheme reduces energy consumption during key updating process.

Multi objective optimization of VPN design by linear programming with risks models

Optimal design of IPsec-based virtual private networks (VPN), in general, depends on multiple factors and parame- ters, such as the VPN's architectural model, hardware and software setups and the technical platform solutions, network topo- logy models, modes of the tunnel's operation, levels of the Open Systems Interconnection (OSI) model, encryption/decryption algorithms, modes of cipher operation, security protocols, security associations and key management techniques, connectivity modes, parameters of security algorithms, computer architectures, the number of tunnels in the VPN, and other factors. This paper presents an innovative approach to using methods of linear programming with risks to solve a multi objective optimiza- tion problem of VPN design. In particular, it describes the proposed conceptual VPN design model, VPN information security space, index of effectiveness for multi objective optimization, a new classification of scales, a system-based approach to risks and mathematical modeling of a risk, a hierarchy of scripts and a theorem of description of passwords, VPN design optimization process and particular procedures, sets of legal and illegal VPN design methods, and a VPN design optimization algorithm based on multi objective optimization by linear programming with risks models. The proposed and developed VPN design optimization algorithm was tested by developing specific VPN design methods for various types of VPN users.

Practical Forward-Secure Range and Sort Queries with Update-Oblivious Linked Lists

Abstract We revisit the problem of privacy-preserving range search and sort queries on encrypted data in the face of an untrusted data store. Our new protocol RASP has several advantages over existing work. First, RASP strengthens privacy by ensuring forward security: after a query for range [a, b], any new record added to the data store is indistinguishable from random, even if the new record falls within range [a, b]. We are able to accomplish this using only traditional hash and block cipher operations, abstaining from expensive asymmetric cryptography and bilinear pairings. Consequently, RASP is highly practical, even for large database sizes. Additionally, we require only cloud storage and not a computational cloud like related works, which can reduce monetary costs significantly. At the heart of RASP, we develop a new update-oblivious bucket-based data structure. We allow for data to be added to buckets without leaking into which bucket it has been added. As long as a bucket is not explicitly queried, the data store does not learn anything about bucket contents. Furthermore, no information is leaked about data additions following a query. Besides formally proving RASP’s privacy, we also present a practical evaluation of RASP on Amazon Dynamo, demonstrating its efficiency and real world applicability.

Cube Attack on Stream Ciphers using a Modified Linearity Test

There have been various attempts to attack reduced variants of Trivium stream cipher using cube attack. During the preprocessing phase of cube attack, we need to test the linearity of a superpoly. The linearity testing problem is to check whether a function is close to linear by asking oracle queries to the function. This is the BLR linearity test for Boolean functions, which has a time complexity of O(22k + c) cipher operations, where k is the length of the key and c is the size of the cube. In this paper we present a method which is supposed to be a sufficient condition for testing a superpoly for linearity in F2 with a time complexity O(2c + 1 (k2 + k)). Our analysis on Trivium cipher reduced to 576 rounds using cube attack gives 69 extremely sparse linearly independent linear equations for smaller cubes, which recovers 69 bits of the key and reduces the attack complexity in the online phase to 211.

An Efficient Approach for Privacy Preserving Distributed Clustering in Semi-honest Model Using Elliptic Curve Cryptography

In this paper, we propose an approach that illustrates the application of Elliptic Curve Cryptography (ECC) in Privacy-preserving distributed K-Means Clustering over horizontally partitioned dataset. We believe that the conventional cryptographic approaches and secret sharing schemes for privacy-preserving distributed K-Means clustering, are not scalable due to the higher computational and communication cost. Elliptic Curve based cryptosystems offer much better key size to security ratio in comparison. Hence, we use ECC based ElGamal scheme in distributed K-Means clustering to preserve privacy. Our approach avoids multiple cipher operations at each site and hence is efficient in terms of computational cost. We also achieve a reduction in the communication cost by allowing parties to communicate in a ring topology. Our experimental results show that our approach is scalable in terms of dataset size and number of parties in a distributed scenario. We carry out comparative analysis of our approach with existing approaches to highlight the effectiveness of our approach.

CipherXRay: Exposing Cryptographic Operations and Transient Secrets from Monitored Binary Execution

Malwares are becoming increasingly stealthy, more and more malwares are using cryptographic algorithms (e.g., packing, encrypting C&C communication) to protect themselves from being analyzed. The use of cryptographic algorithms and truly transient cryptographic secrets inside the malware binary imposes a key obstacle to effective malware analysis and defense. To enable more effective malware analysis, forensics, and reverse engineering, we have developed CipherXRay - a novel binary analysis framework that can automatically identify and recover the cryptographic operations and transient secrets from the execution of potentially obfuscated binary executables. Based on the avalanche effect of cryptographic functions, CipherXRay is able to accurately pinpoint the boundary of cryptographic operation and recover truly transient cryptographic secrets that only exist in memory for one instant in between multiple nested cryptographic operations. CipherXRay can further identify certain operation modes (e.g., ECB, CBC, CFB) of the identified block cipher and tell whether the identified block cipher operation is encryption or decryption in certain cases. We have empirically validated CipherXRay with OpenSSL, popular password safe KeePassX, the ciphers used by malware Stuxnet, Kraken and Agobot, and a number of third party softwares with built-in compression and checksum. CipherXRay is able to identify various cryptographic operations and recover cryptographic secrets that exist in memory for only a few microseconds. Our results demonstrate that current software implementations of cryptographic algorithms hardly achieve any secrecy if their execution can be monitored.

LFSR Multi-Step Parallel Update Technology Utilizing Divider Circuit

In this paper, operation needs and characteristic of LFSR multi-step parallel update technology based on divider circuit design are analyzed. LFSR status switch parallel update principle based on division and serial input parallel update principle are studied to solve multi-step parallel update data generation of LFSR utilizing division. Through hardware implementation and performance analysis, the hardware circuit using LFSR multi-step parallel update operation principle based on division has some advantages, such as more flexibility and high cipher operation performance. It is a better LFSR multi-step parallel update operational model.

A related key impossible differential attack against 22 rounds of the lightweight block cipher LBlock

LBlock is a new lightweight block cipher proposed by Wu and Zhang (2011) [12] at ACNS 2011. It is based on a modified 32-round Feistel structure. It uses keys of length 80 bits and message blocks of length 64 bits.In this letter, we examine the security arguments given in the original article and we show that we can improve the impossible differential attack given in the original article on 20 rounds by constructing a 22-round related key impossible differential attack that relies on intrinsic weaknesses of the key schedule. This attack has a complexity of 270 cipher operations using 247 plaintexts. This result was already published in Minier and Naya-Plasencia (2011) [9].

Energy efficiency of encryption schemes applied to wireless sensor networks

ABSTRACTIn this paper, we focus on the energy efficiency of secure communication in wireless sensor networks (WSNs). Our research considers link layer security of WSNs, investigating both the ciphers and the cryptographic implementation schemes, including aspects such as the cipher mode of operation and the establishment of initialization vectors (IVs). We evaluate the computational energy efficiency of different symmetric key ciphers considering both the algorithm characteristics and the effect of channel quality on cipher synchronization. Results show that the computational energy cost of block ciphers is less than that of stream ciphers when data are encrypted and transmitted through a noisy channel. We further investigate different factors affecting the communication energy cost of link layer cryptographic schemes, such as the size of payload, the mode of operation applied to a cipher, the distribution of the IV, and the quality of the communication channel. A comprehensive performance comparison of different cryptographic schemes is undertaken by developing an energy analysis model of secure data transmission at the link layer. This model is constructed considering various factors affecting both the computational cost and communication cost, and its appropriateness is verified by simulation results. In conclusion, we recommend using a block cipher instead of a stream cipher to encrypt data for WSN applications and using a cipher feedback scheme for the cipher operation, thereby achieving energy efficiency without compromising the security in WSNs. Copyright © 2011 John Wiley & Sons, Ltd.