CFB Mode Research Articles

Improvement in Resilience of AES Design With Reconfigured CFB Mode Against Power Attacks

Improvement in Resilience of AES Design With Reconfigured CFB Mode Against Power Attacks

Discrete Hyperchaotic S-Box Generation for Selective Video Frames Encryption

Cloud computing has become a significant technology with rapid popularization offering many services with highly effective computation and large-scale storage solutions. As multimedia files are growing explosively, securely storing them for authorized access is a major task. Concentrating on video file storage in a public cloud environment, the security and privacy of those outsourced videos are the major concerns. A selective frame encryption approach is proposed to encrypt the semantic elements of the selected frames of High Efficiency Video Coding (HEVC) compressed videos by storing them in the cloud. The semantic elements of HEVC videos are extracted and encrypted by a modified Advanced Encryption Standard (AES) operation in CFB mode with a Substitution-Box (S-Box). A dynamic, nonlinear 2D discrete hyperchaotic mapping-based S-box generation method is proposed to enhance security by providing good confusion, diffusion, and scrambling. The performance analysis of generated S-box and experimental results show that the proposed selective encryption highly resists attacks and encrypts with reduced time complexity.

CFB-Then-ECB Mode-Based Image Encryption for an Efficient Correction of Noisy Encrypted Images

During the last few decades, the transmission of images over secure networks has exponentially grown. Data security in certain applications such as secure storage, authentication or privacy protection on cloud platforms, require specific strategies for multimedia. Cryptography can be used for this purpose. Indeed, using a secret key, it is possible to make data unreadable in order to secure it. Although encryption approaches are effective to make the original data unreadable, they are also very sensitive to noise. Because of the introduction of noise into an encrypted image during its transmission or storage, the original data cannot be recovered. In this article, we first describe a new encryption mode called CFB-then-ECB and based on a combination of the CFB mode and the ECB mode for AES encryption. Using this new encryption mode, if one encrypted pixel block is noised, this will result in two incorrectly reconstructed pixel blocks during the decryption (the current and the following pixel blocks). This noise spreading is then exploited in a new proposed approach of noisy encrypted image correction. It contains two main steps involving a classifier to discriminate clear and encrypted pixel blocks. After a direct decryption of a noisy encrypted image, the first step is to identify and localize the pixel blocks that are probably incorrectly decrypted. The second step of our proposed approach is to analyze and correct these pixel blocks. Experimental results show that the proposed method can be used to blindly correct noisy encrypted images, while preserving the image structure without increasing the original data size with additional information.

Operation of a 1 MWth calcium looping pilot plant firing waste-derived fuels in the calciner

The calcium looping (CaL) process is a promising second-generation carbon capture technology for post-combustion CO2 capture from power and industrial plants. The CO2 in a flue gas stream is captured by means of the reversible carbonation reaction. The CaL process is based on two coupled circulating fluidized bed reactors (carbonator and calciner) using natural limestone as sorbent. Until now, remarkable progress has been made in terms of long-term CaL pilot testing and evaluation in various test rigs. Mainly fossil fuels have been applied as supplementary heat source in the calciner. This work presents first results from long-term pilot testing of the CaL process in the 1 MWth CaL pilot plant at Technische Universität Darmstadt, firing solid recovered fuels under real oxy-fuel conditions in the calciner. The flue gas to be decarbonized in the carbonator was supplied by on-site combustion of pulverized lignite or natural gas. The CO2 concentration in the resulting flue gas stream to be decarbonized in the carbonator was adjusted according to typical values of waste-to-energy plants. During the experimental campaigns, two types of solid recovered fuel were investigated. The lower heating value of the SRF was approximately 21 MJ/kg for the first and approximately 16 MJ/kg for the second type. Overall, the plant was operated over 230 h in interconnected CFB mode, while firing SRF. The process evaluation is based on a simplified reactor model, which is typically applied in the field of CaL technology. It was experimentally proven that carbonator CO2 absorption rates close to the theoretical maximum are feasible while firing SRF in the calciner. Furthermore, it was found that accumulation and distribution of coarse SRF ash fraction in the solid looping system are a key challenge to be addressed in the design stage and operation of a SRF-fired CaL system.

LawCrypt: Secret Sharing for Attorney-Client Data in a Multi-Provider Cloud Architecture

The accelerated employment of cloud computing among law firms is due to multiple benefits, including wide accessibility and inter-organizational information sharing. Nevertheless, the project’s preliminary case study revealed lawyers’ mass neglect of standard precautionary measures and, consequently, a high proportion of security breaches, putting confidential and important documents at risk. The goal of the multi-provider cloud secret sharing architecture was to ensure confidentiality, availability, and integrity of attorney documents while maintaining greater efficiency than traditional encryption algorithms. After an exhaustive development phase involving considerable testing and optimizations, software assessments of the architecture indicate the low computational overhead of adding the secret-sharing approach to a multi-provider law firm sharing environment. The efficient combination of constructions satisfies the engineering criteria as ChaCha20-Poly1305 warrants authenticity and privacy, and secret sharing ensures availability and perfect privacy. Compared with AES in CFB mode, widely used for encrypting data in the Cloud today, the secret sharing implementation boasts almost a 40% improvement over all file sizes. The only possible way of compromising this system is if multiple cloud providers collude, which is still unlikely given that the documents are additionally encrypted.

Ransomware Attack using AES Encryption on ECB, CBC and CFB Mode

With the help of internet, users are faster getting data that they needed. It’s possible that villain insert an evil program (malware) without user knowing it. One of the malwares that spread like a plague right now is ransomware. The infected computer system will encrypt all files on the computer and blackmail the users to pay some money if you want to access back your files. For this experiment it’s using 2 approach, first is using online attack and second is offline attack. Ransomware in this experiment is using AES 256 for encrypting the files and using ECB, CBC and CFB mode for comparing time. As the result ECB is 39.5% faster than CBC and 7,17% faster than CFB. For CFB is 34,83% faster than CBC.

An Enhancement Method Based on Modifying CFB Mode for Key Generation in AES Algorithm

There are two very important characteristics in the block cipher, the amount of time for encryption process and key complexity which caused increasing the complexity of encryption process. This research aims to enhance the key generation of Advanced Encryption Standard (AES) algorithm with high efficiency. The proposed enhancement method architecture based on modifying cipher feedback (MCFB) mode which produce key block from each key generation step in addition to represent current output that is repeated lyre used as input to produce next key block. In the block cipher encryption step, two processes are implemented: Substitution bytes process and Shift rows process. This proposed method improves the performance, efficiency, and speed of the encryption algorithm.

CFB 모드에 기반한 2 차원 페이지 데이터의 광학적 암호화 응용

CFB 모드에 기반한 2 차원 페이지 데이터의 광학적 암호화 응용

The Design and Analysis of the Key-Stream Generator Based on the AES

The key-stream generator is the most important algorithm component of the stream cipher. At the present, it is an important development direction of the stream cipher algorithm that uses complex block cipher algorithms to construct high performance key-stream generators. The paper puts forward a new design method of the key-stream generator based on the AES algorithm. This method is based on the CFB mode of the AES algorithm, combined with the variable-step feedback shift. Then the paper analyses the randomness of the key-stream produced by the new key-stream generator. This new key-stream generator really improves the cryptographic properties of the key stream generator and to enhance the security of stream cipher.

기밀성과 무결성이 우수한 SHACAL-2 기반 스트림 암호 설계 및 구현

5단계 파이프라인으로 구성된 기밀성과 무결성이 우수하고 실시간처리가 가능한 128비트 출력 스트림 암호를 개발했다. 개발한 스트림 암호는 ASR 277비트와 SHACAL-2를 통해 128비트 스트림을 만들고 이를 CFB모드 적용한 후 표백처리 과정을 통하여 최종적인 128비트 암호문을 만드는 스트림 암호 알고리즘이다. 스트림 암호의 하드웨어는 Verilog HDL을 사용하여 Modelsim 6.5d를 활용하여 기능을 검증하였고, 성능은 Quartus II 12.0을 활용하여 분석했고, Worst Case에서 Max Frequency는 33.34MHz(4.27Gbps)의 빠른 성능을 보여주었다. 이는 무선 인터넷과 센서 네트워크 및 DRM 환경의 속도를 충분히 만족함을 보여준다. 기밀성과 무결성이 우수한 스트림 암호 알고리즘 개발에 본 논문은 매우 유용한 아이디어를 제공하고 있다. We have developed a 128-bit stream cipher algorithm composed of the 5-stage pipeline, capable of real-time processing, confidentiality and integrity. The developed stream cipher is a stream cipher algorithm that makes the final 128-bit ciphers through a whitening process after making the ASR 277 bit and SHACAL-2 and applying them to the CFB mode. We have verified the hardware performance of the proposed stream cipher algorithm with Modelsim 6.5d and Quartus II 12.0, and the result shows that the hardware runs at 33.34Mhz(4.27Gbps) at worst case. According to the result, the new cipher algorithm has fully satisfied the speed requirement of wireless Internet and sensor networks, and DRM environment. Therefore, the proposed algorithm with satisfaction of both confidentiality and integrity provides a very useful ideas.

Selective encryption techniques of JPEG2000 codestream for medical images transmission

In this paper, novel selective encryption image schemes based on JPEG2000 are proposed. The first one encrypts only the code-blocks corresponding to some sensitive precincts. In order to improve the security level we introduce the permutation of codeblocks contributing in the selected precincts. The idea of combining permutation and selective encryption is used in order to minimize the amount of processed data encryption while ensuring the best possible degradation through the permutation. Many of proposals format compliant encryption schemes for JPEG2000 that have been made encrypt packet body data, but leave header packet in plaintext. The second approach, combines code-blocks data encryption to a cyclic permutation of all packets headers in the bitstream. Actually, in the JPEG2000 codestream, packet header information is specific to the visual content, and it is can be used as a fingerprint of the codestream. Symmetric encryption AES with CFB mode is used to encrypt in the two schemes. The proposed schemes don't introduce superfluous JPEG2000 markers in the protected codestream, i.e, its format is compliant to JPEG2000 codestream one. It keeps file format and compression ratio unchanged and doesn't degrade the original error robustness. The proposed scheme works with any standard ciphers and introduces negligible computational cost.

CFB air-blown flash pyrolysis. Part II: Operation and experimental results

The main operational characteristics of a novel gasifier operating in the CFB mode are outlined in this paper, based on the experimental results from a total of 11 runs in the pyrolysis mode. The operation runs constituted the main experiments in the CFB reactor, carried out to derive meaningful mass balance and additional operational data for the CFB pyrolyzer. The experiments were conducted in varying operating conditions determined by the most important parameters, i.e., biomass flowrate, fluidizing gas flowrate, air factor, initial bed inventory), temperature in the CFB riser, vapor residence time and nominal air factor – or equivalence ratio, Sb. The results obtained showed that the reactor configuration successfully operated as a biomass fast pyrolysis system to maximize liquid yields reaching 61.50 wt% on a maf biomass basis, with the novel feature of providing for autothermal operation at 500 °C and with 0.46 s gas–vapor residence time, by utilizing the by-product char energy content in a single reactor. The reactor provides a very high specific throughput of 1.12–1.48 kg/h m2 and the lowest gas-to-feed ratio of 1.3–1.9 kg gas/kg feed compared to other fast pyrolysis processes based on pneumatic reactors and has a good scale-up potential, providing significant capital cost reduction. Results to date suggest that the process is limited by the extent of char combustion. Future work should address resizing of the char combustor to increase overall system capacity, improve the solid separation and substantially increase liquid recovery.