Bitstream Encryption Research Articles

On the Security of Selectively Encrypted HEVC Video Bitstreams

With the growing applications of video, ensuring its security has become of utmost importance. Selective encryption (SE) has gained significant attention in the field of video content protection due to its compatibility with video codecs, favorable visual distortion, and low time complexity. However, few studies consider SE security under cryptographic attacks. To fill this gap, we analyze the security concerns of encrypted bitstreams by SE schemes and propose two known plaintext attacks (KPAs). Then the corresponding defense is presented against the KPAs. To validate the effectiveness of the KPA, it is applied to attack two existing SE schemes with superior visual degradation in HEVC videos. Firstly, the video sequences are encoded using H.265/HEVC. During encoding, the selected syntax elements are recorded. Secondly, the recorded syntax elements are imported into the HEVC decoder. By utilizing the encryption parameters and the imported data in the decoder, it becomes possible to reconstruct a significant portion of the original syntax elements before encryption. Finally, the reconstructed syntax elements are compared with the encrypted syntax elements in the decoder, allowing the design of a pseudo-key stream (PKS) through the inverse of the encryption operations. The PKS is used to decrypt the existing SE scheme, and the experimental results provide evidence that the two existing SE schemes are vulnerable to the proposed KPAs. In the case of single bitstream estimation (SBE), the average correct rate of key stream estimation exceeds 93%. Moreover, with multi-bitstream complementation (MBC), the average estimation accuracy can be further improved to 99%.

Faster abnormality localization and recognition in a secured video bitstream by implementation of video encryption techniques

Cloud video storage uses an encrypted format to protect user data. It means encrypted video processing is an essential part of secured cloud storage. In order to detect suspicious or anomalous behavior, video surveillance must have encrypted cloud access. The primary goals of this research are to estimate parameters and detect abnormalities in an encrypted video bitstream. Various typical properties of video encoding frameworks and format-compliant encryption algorithms are investigated to identify abnormalities in an encrypted video bitstream using format-compliant encryption. The encrypted bitstream is decrypted to get three different kinds of enhancement features: the sizes of macroblocks, partitions of macroblocks, and the magnitude of the motion vector. The identification and localization methods now do not include video decryption or complete decompression. The proposed strategy has been created to implement the video encryption scheme efficiently and is compatible with various video encryption techniques. The experimental findings demonstrate that, in comparison to other methods, the proposed approach provides optimal running time and detection rate performance.

An Innovative FPGA Implementations of the Secure Frequency Hopping Communication System Based on the Improved ZUC Algorithm

Frequency Hopping (FH) is a significant anti-interception and anti-interference, so some wireless communication systems extensively use it. Then it can offer better security performance of the system via combining cryptographic algorithms with FH. This paper presents a detailed theoretical design and hardware implementation of an evolutionary ZUC stream cipher algorithm on FPGA. Using some encryption algorithms can improve the security of the FH system by increasing its complexity, including SNOW3g, ZUC algorithm, Chaos system, and other cipher methods. ZUC (named for Zu Chongzhi, a famous mathematician in ancient China) is bitstream encryption that builds the core of the 3GPP integrity algorithm 128-EIA3 and the 3GPP confidentiality algorithm 128-EEA3, providing authentic security services in 4G, even in 5G (IMT-2020) to some extent. The article presented an evolutionary three-layers structure of the ZUC FH system, which innovatively applied the permutation polynomial algorithm and an evolutionary DES cipher algorithm. The introduction of that new DES and the permutation polynomial can efficiently increase the security performance of the ZUC system but also avoid some shortcomings of the UHF (Ultra High Frequency) communication. The experiment of this research designed software by coding VHDL language and implemented hardware using a XILINX Virtex-5 FPGA. The finished experiment gave, analyzed, and compared all results according to the performance of the proposed system and hardware resources. The tests for evaluating the randomness and security denote that the constructed sequences have better performance, including the randomness, linear complexity, and hamming correlations, and pass the NIST test finally. The experimental results show that this improved ZUC cipher stream algorithm proposed in the article can provide a high throughput of 2.08 Gbps under a 65MHz clock frequency. The authors will focus their future work on applying the evolutionary S-box and the algorithm with better security performance.

Selective Encryption of the Versatile Video Coding Standard

versatile video coding (VVC) is the next generation video coding standard developed by the joint video experts team (JVET) and released in July 2020. VVC introduces several new coding tools providing a significant coding gain over the high efficiency video coding (HEVC) standard. It is well known that increasing the coding efficiency adds more dependencies in the video bitstream making format-compliant encryption with the standard more challenging. In this paper we tackle the problem of selective encryption of the VVC standard in format-compliant and constant bitrate. These two constraints ensure that the encrypted bitstream can be decoded by any VVC decoder while the bitrate remains unchanged by the encryption. The selective encryption of all possible VVC syntax elements is investigated. A new algorithm is proposed to encrypt in format-compliant and constant bitrate the transform coefficients (TCs) together with other syntax elements at the level of the entropy encoder. The proposed solution was integrated and assessed under the VVC reference software model version 6.0. Experimental results showed that encryption drastically decreases the video quality while the encryption is robust against several types of attacks. The encryption space is estimated in the range of 15% to 26% of the bitstream size resulting in a lightweight encryption process. The web page of this work is publicly available at <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://gugautie.github.io/sevvc/</uri> .

Cryptanalysis of Start Code-Based Encryption Method for HEVC

We propose a cryptanalysis for MPEG high efficiency video coding bitstream encryption based on the start code. Today, most digital video data are transmitted over an open Internet network in an encrypted state for security and privacy. In general, video services must guarantee real-time communications; therefore, it is necessary to reduce the computational complexity required to encrypt video data. Consequently, many selective encryption algorithms that selectively encrypt a highly sensitive part of the entire video data have been studied. Recently, we proposed a selective encryption algorithm based on the start code for high efficiency video coding, which dramatically reduces the computational complexity of encryption. In this paper, we studied the cryptanalysis of the encryption algorithm based on the start code and found a security vulnerability for a ciphertext-only attack. The proposed method presents a method to restore the encrypted first byte of the network abstraction layer unit header by analyzing the unencrypted high efficiency video coding bitstream. The first byte of the network abstraction layer unit header can be restored using the unencrypted parts, such as the order, syntax element, and length of the network abstraction layer unit. The experimental results demonstrated the security vulnerability by breaking the start code based encryption algorithm that is difficult to recover using the brute-force attack with only one to six recovery attempts using the proposed ciphertext-only attack.

Efficient Privacy-Preserving Anomaly Detection and Localization in Bitstream Video

In cloud computing, videos may be in an encrypted format to protect privacy. Therefore, encrypted video processing is an important application in secure cloud computing. In this paper, we focus on parameter estimation and anomaly detection in an encrypted video bitstream. By analyzing the common properties of video encoding frameworks and the format-compliant encryption schemes, we propose an anomaly detection scheme for encrypted video bitstream with format-compliant encryption. From the encrypted bitstream, we extract three types of complementary features, i.e., the macroblock sizes, the macroblock partitions, and the motion vector difference magnitude, and then propose a method to combine these three features. The proposed detection and localization scheme does not involve video decryption, full decompression, or an interactive protocol, which makes it efficient. Our scheme is also compatible with different video encryption methods. To accelerate the running time, we develop a parallel implementation for our scheme. The experimental results show that our method achieves good running time and detection rate performance.

Secure hardware-entangled field programmable gate arrays

The configuration bitstream is a persistent source of vulnerability in FPGA designs, and thus FPGA vendors have implemented bitstream encryption. A number of attacks on these countermeasures have been demonstrated including direct probing of the configuration storage cells, side-channel attacks on the decryption blocks, and attacks on the scan chain. Thus, we present an FPGA design that never stores the configuration data in the clear, even at the lowest level of the hardware. We deeply hardware entangle the reconfigurable logic and interconnect by one time pad encrypting the bitstream using a PUF response. By leveraging recent work in high performance, high density, high reliability, and low power PUF design, we tightly integrate a PUF bit with every configuration bit. This has significant security benefits including high resistance to probing attacks and unique per-die configuration bitstreams, while only requiring minor modification of the FPGA design. Based on overheads from a PUF implementation in an industrial 65 nm bulk CMOS process, we simulate such an FPGA design and achieve modest overheads in power, area, and performance across multiple security-focused benchmark applications, as well as various MCNC benchmark circuits from a variety of real applications.

Reliable and Modeling Attack Resistant Authentication of Arbiter PUF in FPGA Implementation With Trinary Quadruple Response

Field programmable gate array (FPGA) is a potential hotbed for malicious and counterfeit hardware infiltration. Arbiter-based physical unclonable function (A-PUF) has been widely regarded as a suitable lightweight security primitive for FPGA bitstream encryption and device authentication. Unfortunately, the metastability of flip-flop gives rise to poor A-PUF reliability in FPGA implementation. Its linear additive path delays are also vulnerable to modeling attacks. Most reliability enhancement techniques tend to increase the response predictability and ease machine learning attacks. This paper presents a robust device authentication method based on the FPGA implementation of a reliability enhanced A-PUF with trinary digit (trit) quadruple responses. A two flip-flop arbiter is used to produce a trit for metastability detection. By considering the ordered responses to all four combinations of first and last challenge bits, each quadruple response can be compressed into a quadbit that represents one of the five classes of trit quadruple response with greater reproducibility. This challenge-response quadruple classification not only greatly reduces the burden of error correction at the device but also enables a precise A-PUF model to be built at the server without having to store the complete challenge-response pair (CRP) set for authentication. Besides, the real challenge to the A-PUF is generated internally by a lossy, nonlinear, and irreversible maximum length signature generator at both the server and device sides to prevent the naked CRP from being machine learned by the attacker. The A-PUF with short repetition code of length five has been tested to achieve a reliability of 1.0 over the full operating temperature range of the target FPGA board with lower hardware resource utilization than other modeling attack resilient strong PUFs. The proposed authentication protocol has also been experimentally evaluated to be practically secure against various machine learning attacks including evolutionary strategy covariance matrix adaptation.

New Framework of Reversible Data Hiding in Encrypted JPEG Bitstreams

This paper proposes a novel framework of reversible data hiding in encrypted JPEG bitstream. We first provide a JPEG encryption algorithm to encipher a JPEG image to a smaller size and keep the format compliant to JPEG decoders. After an image owner uploads the encrypted JPEG bitstreams to cloud storage, the server embeds additional messages into the ciphertext to construct a marked encrypted JPEG bitstream. During data hiding, we propose a combined embedding algorithm including two stages, the Huffman code mapping and the ordered histogram shifting. The embedding procedure is reversible. When an authorized user requires a downloading operation, the server extracts additional messages from the marked encrypted JPEG bitstream and recovers the original encrypted bitstream losslessly. After downloading, the user obtains the original JPEG bitstream by a direct decryption. The proposed framework outperforms previous works on reversible data hiding in encrypted images. First, since the tasks of data embedding/extraction and bitstream recovery are all accomplished by the server, the image owner and the authorized user are required to implement no extra operations except JPEG encryption or decryption. Second, the embedding payload is larger than state-of-the-art works.

An Autonomous, Self-Authenticating, and Self-Contained Secure Boot Process for Field-Programmable Gate Arrays

Secure booting within a field-programmable gate array (FPGA) environment is traditionally implemented using hardwired embedded cryptographic primitives and non-volatile memory (NVM)-based keys, whereby an encrypted bitstream is decrypted as it is loaded from an external storage medium, e.g., Flash memory. A novel technique is proposed in this paper that self-authenticates an unencrypted FPGA configuration bitstream loaded into the FPGA during the start-up. The internal configuration access port (ICAP) interface is accessed to read out configuration information of the unencrypted bitstream, which is then used as input to a secure hash function SHA-3 to generate a digest. In contrast to conventional authentication, where the digest is computed and compared with a second pre-computed value, we use the digest as a challenge to a hardware-embedded delay physical unclonable function (PUF) called HELP. The delays of the paths sensitized by the challenges are used to generate a decryption key using the HELP algorithm. The decryption key is used in the second stage of the boot process to decrypt the operating system (OS) and applications. It follows that any type of malicious tampering with the unencrypted bitstream changes the challenges and the corresponding decryption key, resulting in key regeneration failure. A ring oscillator is used as a clock to make the process autonomous (and unstoppable), and a novel on-chip time-to-digital-converter is used to measure path delays, making the proposed boot process completely self-contained, i.e., implemented entirely within the re-configurable fabric and without utilizing any vendor-specific FPGA features.

Bitstream Fault Injections (BiFI)–Automated Fault Attacks Against SRAM-Based FPGAs

This contribution is concerned with the question whether an adversary can automatically manipulate an unknown FPGA bitstream realizing a cryptographic primitive such that the underlying secret key is revealed. In general, if an attacker has full knowledge about the bitstream structure and can make changes to the target FPGA design, she can alter the bitstream leading to key recovery. However, this requires challenging reverse-engineering steps in practice. We argue that this is a major reason why bitstream fault injection attacks have been largely neglected in the past. In this paper, we show that malicious bitstream modifications are i) much easier to conduct than commonly assumed and ii) surprisingly powerful. We introduce a novel class of bitstream fault injection (BiFI) attacks which does not require any reverse-engineering. Our attacks can be automatically mounted without any detailed knowledge about either the bitstream format or the design of the crypto primitive which is being attacked. Bitstream encryption features do not necessarily prevent our attack if the integrity of the encrypted bitstream is not carefully checked. We have successfully verified the feasibility of our attacks in practice by considering several publicly available AES designs. As target platforms, we have conducted our experiments on Spartan-6 and Virtex-5 Xilinx FPGAs.

Reversible Data Hiding in Encrypted Three-Dimensional Mesh Models

Reversible data hiding in encrypted domain (RDH-ED) has greatly attracted researchers as the original content can be losslessly reconstructed after the embedded data are extracted, while the content owner's privacy remains protected. Most of the existing RDH-ED algorithms are designed for grayscale/color images, which cannot be directly applied to other carriers, such as three-dimensional (3D) meshes. With the rapid development of 3D related applications, 3D models have been widely used on the Internet, which motivated us to design a reliable RDH-ED scheme for 3D meshes. The proposed method maps decimals of the vertex coordinates into integers first, so that a bit-stream encryption technique can be executed. With a data-hiding key, several least-significant bits are operated to embed data. By using the encryption key, a receiver can roughly reconstruct the content of the mesh. According to the data-hiding key, with the aid of spatial correlation in natural mesh models, the embedded data can be successfully extracted and the original mesh can be perfectly recovered. Experiments show that the proposed method has a high data-embedding payload, maintains high values of the decrypted meshes, and has low computational complexity.

A separable reversible data hiding scheme for encrypted JPEG bitstreams

In this paper, we construct a separable reversible data hiding scheme for encrypted JPEG bitstreams. Our proposed scheme is constructed via a reserving-room-before-encryption manner, that is, the original JPEG bitstream is modified with small distortion so that the content owner can reserve enough space for future data embedding and then the modified JPEG bitstream is encrypted. To do that, our key observation is that the least significant bits of the two-bit appended values in the JPEG bitstream is a biased bitstream. Thus we design a new lossless compression algorithm for biased bitstreams with better compression ratio than the binary arithmetic coding method to fulfill the above task for pre-reserving space. With this room-reserving technique, the encrypted JPEG bitstream can be generated and the data embedding in this encrypted bitstream can be done easily by the data hider. Finally, the receiver is able to extract the embedded data and recovers the original JPEG bitstream independently.

Stripping very low frequency communication signals with minimum shift keying encoding from streamed time-domain electromagnetic data

The objective of this research is to eliminate very low frequency (VLF) communication signals with frequencies in the range of 15–25 kHz from streamed time-domain electromagnetic data. The frequency-domain approach of notch filtering or bandwidth limitation is unsatisfactory when early delay-time data are required in a time-domain system. United States military VLF transmitters presently communicate [Formula: see text] using minimum shift keying modulation, and it is possible to derive the encrypted bitstream from the data sampled at typical geophysical streaming rates. The method involves convolving the data with waveforms of frequency different by one-quarter of the bit rate above and below the carrier frequency and using the difference between the convolutions to predict the transmitted bits. The transmitted signal is then exactly recreated from the decoded bits, and the predicted signal at the receiver is subtracted from the data stream. It is possible to predict bit rates and encoding methods from other military transmitters through data analysis and again subtract the predicted signals from the streamed data. This procedure reduces the variance of data, implying that unwanted VLF signals have been reduced by a factor of three to nine in stations thousands of kilometers from a VLF transmitter. Much larger signal/noise improvements are predicted for stations within a few hundred kilometers of the VLF source. Lower degrees of improvement are noted from Indian and Chinese transmitters, which appear to have different encoding and modulation methods.

Context adaptive binary arithmetic coding-based data hiding in partially encrypted H.264/AVC videos

A scheme of data hiding directly in a partially encrypted version of H.264/AVC videos is proposed which includes three parts, i.e., selective encryption, data embedding and data extraction. Selective encryption is performed on context adaptive binary arithmetic coding (CABAC) bin-strings via stream ciphers. By careful selection of CABAC entropy coder syntax elements for selective encryption, the encrypted bitstream is format-compliant and has exactly the same bit rate. Then a data-hider embeds the additional data into partially encrypted H.264/AVC videos using a CABAC bin-string substitution technique without accessing the plaintext of the video content. Since bin-string substitution is carried out on those residual coefficients with approximately the same magnitude, the quality of the decrypted video is satisfactory. Video file size is strictly preserved even after data embedding. In order to adapt to different application scenarios, data extraction can be done either in the encrypted domain or in the decrypted domain. Experimental results have demonstrated the feasibility and efficiency of the proposed scheme.

Robust and fast selective encryption for HEVC videos

Emerging High efficiency video coding (HEVC) is expected to be widely adopted in network applications for high definition devices and mobile terminals. Thus, construction of HEVC's encryption schemes that maintain format compliance and bit rate of encrypted bitstream becomes an active security's researches area. This paper presents a novel selective encryption technique for HEVC videos, based on enciphering the bins of selected Golomb–Rice code’s suffixes with the Advanced Encryption Standard (AES) in a CBC operating mode. The scheme preserves format compliance and size of the encrypted HEVC bitstream, and provides high visual degradation with optimized encryption space defined by selected Golomb–Rice suffixes. Experimental results show reliability and robustness of the proposed technique.

Physical Security Evaluation of the Bitstream Encryption Mechanism of Altera Stratix II and Stratix III FPGAs

To protect Field-Programmable Gate Array (FPGA) designs against Intellectual Property (IP) theft and related issues such as product cloning, all major FPGA manufacturers offer a mechanism to encrypt the bitstream that is used to configure the FPGA. From a mathematical point of view, the employed encryption algorithms (e.g., Advanced Encryption Standard (AES) or 3DES) are highly secure. However, it has been shown that the bitstream encryption feature of several FPGA families is susceptible to side-channel attacks based on measuring the power consumption of the cryptographic module. In this article, we present the first successful attack on the bitstream encryption of the Altera Stratix II and Stratix III FPGA families. To this end, we analyzed the Quartus II software and reverse engineered the details of the proprietary and unpublished schemes used for bitstream encryption on Stratix II and Stratix III. Using this knowledge, we demonstrate that the full 128-bit AES key of a Stratix II as well as the full 256-bit AES key of a Stratix III can be recovered by means of side-channel attacks. In both cases, the attack can be conducted in a few hours. The complete bitstream of these FPGAs that are (seemingly) protected by the bitstream encryption feature can hence fall into the hands of a competitor or criminal—possibly implying system-wide damage if confidential information such as proprietary encryption schemes or secret keys programmed into the FPGA are extracted. In addition to lost IP, reprogramming the attacked FPGA with modified code, for instance, to secretly plant a hardware Trojan, is a particularly dangerous scenario for many security-critical applications.

Secure distribution infrastructure for hardware digital contents

Field-programmable gate array (FPGA) reconfigurability creates the possibility of distributing hardware cores pretty much like software digital contents, possibly on payment or on a subscription basis. In this work, the authors propose an infrastructure for the secure distribution of such hardware digital contents (HDCs). Aimed at the practical realisation of the envisioned scenario, this study analyses the security-related features of the current FPGA devices, for example, (partial) bitstream encryption, and takes them as the underlying constraints for the definition of the infrastructure. This work clearly identifies the roles involved in the secure distribution process, including a trusted third-party entity, and introduces a cryptographic protocol ensuring the confidentiality and the trustworthiness of partial bitstreams dynamically downloaded to the user's device. This study also presents a detailed case-study application scenario, namely the secure distribution of image codec components, providing a few quantitative results and demonstrating the limited overhead incurred by the proposed solution in terms of time and area costs. The conclusive section of this study discusses the lesson learned from this work and draws a few proposals for the evolution of security-related FPGA features which may enable the full realisation of the secure HDC distribution concept.

Reversible Data Hiding in Encrypted JPEG Bitstream

This correspondence proposes a framework of reversible data hiding (RDH) in an encrypted JPEG bitstream. Unlike existing RDH methods for encrypted spatial-domain images, the proposed method aims at encrypting a JPEG bitstream into a properly organized structure, and embedding a secret message into the encrypted bitstream by slightly modifying the JPEG stream. We identify usable bits suitable for data hiding so that the encrypted bitstream carrying secret data can be correctly decoded. The secret message bits are encoded with error correction codes to achieve a perfect data extraction and image recovery. The encryption and embedding are controlled by encryption and embedding keys respectively. If a receiver has both keys, the secret bits can be extracted by analyzing the blocking artifacts of the neighboring blocks, and the original bitstream perfectly recovered. In case the receiver only has the encryption key, he/she can still decode the bitstream to obtain the image with good quality without extracting the hidden data.

Visual Protection of HEVC Video by Selective Encryption of CABAC Binstrings

This paper presents one of the first methods allowing the protection of the newly emerging video codec HEVC (High Efficiency Video Coding). Visual protection is achieved through selective encryption (SE) of HEVC-CABAC binstrings in a format compliant manner. The SE approach developed for HEVC is different from that of H.264/AVC in several aspects. Truncated rice code is introduced for binarization of quantized transform coefficients (QTCs) instead of truncated unary code. The encryption space (ES) of binstrings of truncated rice codes is not always dyadic and cannot be represented by an integer number of bits. Hence they cannot be concatenated together to create plaintext for the CFB (Cipher Feedback) mode of AES, which is a self-synchronizing stream cipher for so-called AES-CFB. Another challenge for SE in HEVC concerns the introduction of context, which is adaptive to QTC. This work presents a thorough investigation of HEVC-CABAC from an encryption standpoint. An algorithm is devised for conversion of non-dyadic ES to dyadic, which can be concatenated to form plaintext for AES-CFB. For selectively encrypted binstrings, the context of truncated rice code for binarization of future syntax elements is guaranteed to remain unchanged. Hence the encrypted bitstream is format-compliant and has exactly the same bit-rate. The proposed technique requires very little processing power and is ideal for playback on hand held devices. The proposed scheme is acceptable for DRM of a wide range of applications, since it protects the contour and motion information, along with texture. Several benchmark video sequences of different resolutions and diverse contents were used for experimental evaluation of the proposed algorithm. A detailed security analysis of the proposed scheme verified the validity of the proposed encryption scheme for content protection in a wide range of applications.