Subliminal Channel Research Articles

SR-PEKS: Subversion-Resistant Public Key Encryption With Keyword Search

Public key encryption with keyword search (PEKS) provides secure searchable data encryption in cloud storage. Users can outsource encrypted data and keywords to a cloud server, and search target one without disclosing sensitive information. To achieve resistance against off-line keyword guessing attacks, existing practical PEKS schemes employ independent key server(s) to assist users in producing keywords to be encrypted (called server-derived keywords) in an online manner. In this paper, we analyze server-aided PEKS schemes and reveal a potential threat: vulnerability against subversion attacks, where algorithms in server-aided PEKS might be maliciously implemented to undermine security. In a subverted encryption implementation, a subliminal channel is established to control randomness generation such that biased ciphertexts covertly leak plaintext information. We further present a specific subversion attack against generation of server-derived keywords to violate keywords' confidentiality. To address these issues, we propose SR-PEKS, a subversion-resistant PEKS scheme based on cryptographic reverse firewalls (CRF). In SR-PEKS, CRF sanitizes outputs of server-derived keyword generation to resist the presented subversion attack. CRF also participates in a collaborative randomness generation protocol to yield unbiased randomness for encryption, thereby eliminating the subliminal channel. Provable security and high efficiency of SR-PEKS are demonstrated by comprehensive analyses and performance evaluations.

Subliminal Channels in Visual Cryptography

This paper describes three methods of creating a subliminal channel in visual cryptography that are defined for a (2,2) sharing scheme. They work by hiding additional covert information besides the original encrypted image. The first channel is revealed when the user folds the share along the specific axis. The second channel encodes subpixels on the basis of the encrypted message bits. It is designed to hide a wide range of data types. The third channel may be applied to a single share or multiple shares and is revealed when the proper parts of the shares are stacked. Fold and overlapping algorithms are adequate for printed shares, but the encryption method is only suitable for digital shares. The capacity of these methods ranges from half of the image size to the whole image size. The presented algorithms work on black-and-white images but are expandable to color visual cryptography. They may find applications in steganography and other data-hiding techniques. The created subliminal channels do not interfere with regular images that may still be revealed by stacking the shares. In short, this article introduces subliminal channels in visual cryptography, presents three algorithms for both binary and colorful images, shows examples of use with the results obtained, and discusses features of each method.

Algorithm substitution attacks against receivers

This work describes a class of Algorithm Substitution Attack (ASA) generically targeting the receiver of a communication between two parties. Our work provides a unified framework that applies to any scheme where a secret key is held by the receiver; in particular, message authentication schemes (MACs), authenticated encryption (AEAD) and public key encryption (PKE). Our unified framework brings together prior work targeting MAC schemes (FSE’19) and AEAD schemes (IMACC’19); we extend prior work by showing that public key encryption may also be targeted. ASAs were initially introduced by Bellare, Paterson and Rogaway in light of revelations concerning mass surveillance, as a novel attack class against the confidentiality of encryption schemes. Such an attack replaces one or more of the regular scheme algorithms with a subverted version that aims to reveal information to an adversary (engaged in mass surveillance), while remaining undetected by users. Previous work looking at ASAs against encryption schemes can be divided into two groups. ASAs against PKE schemes target key generation by creating subverted public keys that allow an adversary to recover the secret key. ASAs against symmetric encryption target the encryption algorithm and leak information through a subliminal channel in the ciphertexts. We present a new class of attack that targets the decryption algorithm of an encryption scheme for symmetric encryption and public key encryption, or the verification algorithm for an authentication scheme. We present a generic framework for subverting a cryptographic scheme between a sender and receiver, and show how a decryption oracle allows a subverter to create a subliminal channel which can be used to leak secret keys. We then show that the generic framework can be applied to authenticated encryption with associated data, message authentication schemes, public key encryption and KEM/DEM constructions. We consider practical considerations and specific conditions that apply for particular schemes, strengthening the generic approach. Furthermore, we show how the hybrid subversion of key generation and decryption algorithms can be used to amplify the effectiveness of our decryption attack. We argue that this attack represents an attractive opportunity for a mass surveillance adversary. Our work serves to refine the ASA model and contributes to a series of papers that raises awareness and understanding about what is possible with ASAs.

Revisited—The Subliminal Channel in Blockchain and Its Application to IoT Security

Although digital signature has been a fundamental technology for cryptosystems, it still draws considerable attention from both academia and industry due to the recent raising interest in blockchains. This article revisits the subliminal channel existing digital signature and reviews its abuse risk of the constructor’s private key. From a different perspective on the subliminal channel, we find the new concept named the chamber of secrets in blockchains. The found concept, whereby the secret is hidden and later recovered by the constructor from the common transactions in a blockchain, highlights a new way to encourage implementing various applications to benefit efficiency and security. Thus, the proposed scheme benefits from the following advantages: (1) avoiding the high maintenance cost of certificate chain of certificate authority, or public key infrastructure, and (2) seamlessly integrating with blockchains using the property of chamber of secrets. In order to easily understand the superiority of this new concept, a remote authentication scenario is taken as a paradigm of IoT to demonstrate that the further advantages are achieved: (1) avoiding high demand for storage space in IoT devices, and (2) avoiding maintaining a sensitive table in IoT server.

A blockchain-based intelligent anti-switch package in tracing logistics system

In recent years, with the rapid development of e-commerce and network technologies, many people do online shopping through the Internet. If a physical product is bought by a client, the store will entrust their logistics to deliver the goods to the client. However, there have been many cases of switched goods which were purchased by clients recently. Some scholars proposed a security mechanism with a subliminal channel for E-cash and digital content previously. Only the designated sender and the designated receiver know the subliminal message which was hidden in the signature. Thus, it can be applied to solve the switched package issue. According to the WTO (World Trade Organization) forum, blockchain-related logistics applications have gradually emerged in recent days. Blockchain technology is essentially a decentralized database maintained by the collective. It has the characteristics of high reliability and high confidentiality and has a good prospect in effectively solving the trust problem between the two parties. In short, blockchain information will be publicly verifiable and cannot be tampered with, which provides solutions for traditional logistics. It realizes trust and cooperation between multiple entities, and create a modernized logistics environment. In this paper, we attach a sensor to monitor the situation of the delivery object and tag on the package to be an IoT object. The proposed scheme is a blockchain-based intelligent anti-switch package in tracing the logistics system. The client can check the GPS (Global Positioning System) location, the temperature, and humidity sensing data of the package any time during the delivery process, and the IoT-related intelligent logistics can be achieved. The proposed scheme also achieves data integrity, resisting replay attack, forward and backward secrecy, non-repudiation, and mutual authentication.

Efficient Multi-Secret Digital Images Steganography

The new conceptions of more than one secret message and false digital image steganography are presented in the current paper. One of the major ideas in these approaches is embodiment of more than one message in one container (digital image). The secrets that are hidden are known as real and false messages. The former one includes basic data that should be transferred between various parties in a secure manner. The second one is a bait for in order to focus attention on a non-important message. When it is discovered that there exists the actual information, this false and multiple data hidden steganography is cracked, regardless of detection of false message. Many various applications can be found for these concepts, particularly in situations that there is close monitoring over the communication channel between a receiver and a sender and there is suspicion of using steganography. In this case, probably the transferred data would be examined in detailed. The concepts that are defined in the current paper would be helpful for overcoming this problem through ignoring an invented message and thus, deception of the warden. It can be perceived as an additional benefit that it is possible to send both false and real data at the same time. The presented idea actually gives the opportunity of the establishment of a subliminal channel during the transfer of hidden information by the use of digital images.

Development of SETUP-free cryptographic protocols

Today, hybrid cryptosystems are important part in structure of information telecommunication systems. That's why information security measures are extremely crucial at each stage of cryptosystem development life cycle. One of the most important specific of modern cryptosystems is the fact, that they often deployed in unprotected environment and outside the physically secured perimeter. That introduces new attack vectors, e.g. kleptographic attacks which include implementation forgery at endpoints. Such attack types are extremely dangerous because of the victim, who is a participant of some restricted area (electronic document flow, payment system, secure communication etc.), may induce threats for non-compromised participants (e.g., sensitive information leakage). One of the ways to solve mitigate this risks is development subliminal channel free cryptosystems which are resistant against different types of kleptographic attacks. In the article we show results belong to development of SETUP free cryptographic protocol development. Firstly, we suggest formal model for basic ''challenge-response'' protocol with subliminal channel. Using this formal model, we introduce sufficient conditions which lead to impossibility of existence of subliminal channels. Also the theorem about sufficient conditions has been formulated and proved. Further, we suggest improvements of basic protocols -- nonce generation and 1-round Diffie-Hellman key agreement protocol with design that is based of sufficient conditions. Using formalization of suggested enhanced protocols we formulated and proved the theorem about SETUP resistance property for these protocols. Our results may be useful for other SETUP free protocols development, this will be helpful for increasing security of hybrid cryptosystem.

Lightweight and Manageable Digital Evidence Preservation System on Bitcoin

An effective and secure system used for evidence preservation is essential to possess the properties of anti-loss, anti-forgery, anti-tamper and perfect verifiability. Traditional architecture which relies on centralized cloud storage is depressingly beset by the security problems such as incomplete confidence and unreliable regulation. Moreover, an expensive, inefficient and incompatible design impedes the effort of evidence preservation. In contrast, the decentralized blockchain network is qualified as a perfect replacement for its secure anonymity, irrevocable commitment, and transparent traceability. Combining with subliminal channels in blockchain, we have weaved the transaction network with newly designed evidence audit network. In this paper, we have presented and implemented a lightweight digital evidence-preservation architecture which possesses the features of privacy-anonymity, audit-transparency, function-scalability and operation-lightweight. The anonymity is naturally formed from the cryptographic design, since the cipher evidence under encrypted cryptosystem and hash-based functions leakages nothing to the public. Covert channels are efficiently excavated to optimize the cost, connectivity and security of the framework, transforming the great computation power of Bitcoin network to the value of credit. The transparency used for audit, which relates to the proof of existence, comes from instant timestamps and irreversible hash functions in mature blockchain network. The scalability is represented by the evidence chain interacted with the original blockchain, and the extended chains on top of mainchain will cover the most of auditors in different institutions. And the lightweight, which is equal to low-cost, is derived from our fine-grained hierarchical services. At last, analyses of efficiency, security, and availability have shown the complete accomplishment of our system.

An Electronic Public Engineering Project Bidding Protocol via a Subliminal Channel

Due to the rapid development of the Internet, many applications of Internet are widely used. Therefore, the security issue of Internet has become an important issue. In this paper, we proposed an electronic public engineering project bidding protocol via subliminal channel can protect bidder's benefit. On the other hand, we offer an official agent to make a fair arbitration. Our scheme not only satisfies non-repudiation, untraceable and fair arbitration of the public engineering project, but also can resist replay attack, forgery attack and insider attack. Our scheme enhances security and fairness. DOI: http://dx.doi.org/10.5755/j01.itc.46.4.14163

False and multi-secret steganography in digital images

This paper presents the new concepts of multi-secret and false digital image steganography. The main idea of such approaches is to embed in a single container (digital image) more than one message. The hidden secrets are called real and false messages, respectively. The first one contains essential data which are intended to be securely transferred between different parties, the latter is a bait for focusing attention on an unimportant message. This false and multi-secret steganography will be broken when existence of the real message is revealed, it does not matter whether the false message is detected. Such concepts may find many different applications, especially in situations where communication channel between a sender and a receiver is closely monitored and the warden suspects that the steganography is used. In that case it is probable that the transmitted data will be analyzed in a very detailed way. The concepts described in this paper can help to overcome this problem by dropping a fabricated message and thereby deceiving the warden. The possibility of sending both real and false information at the same time can be seen as additional benefit. In fact, the presented idea allows to establish a kind of subliminal channel while transferring hidden information using digital images.

Fault-injection based backdoors in Pseudo Random Number Generators

The main aim of this paper is to present the concept of fault-injection backdoors in Random Number Generators. Backdoors can be activated by fault-injection techniques. Presented algorithms can be used in embedded systems like smart-cards and hardware security modules in order to implement subliminal channels in random number generators.

On the Existence of Subliminal Channel in Instant Messaging Systems

Subliminal channel is a covert communication channel that can securely exchange secret information. By analyzing the communication protocols and encryption algorithms of two popular instant messaging systems QQ and Skype, this paper devotes the efforts to find whether they satisfy the condition of establishing subliminal channel or not. The broad-band subliminal channel can be established in Skype and QQ messages. Therefore, two subliminal channel schemes are proposed to embed and extract subliminal information. Finally, performances of the proposed subliminal channels are compared with those of the ones based on ElGamal digital signature and Newton channel. Experimental results and theoretical analysis show that they are easy to be implemented with large bandwidth and execute fast.

Applying Information Hiding in VANETs to Covertly Report Misbehaving Vehicles

Vehicular ad hoc networks (VANETs) are a new communication scenario in which vehicles take an active part. Real-time reporting of misbehaving vehicles by surrounding ones is enabled by in-vehicle sensors and VANETs. Thus, sensors allow detecting the misbehavior whereas VANETs allow sending the report to the authority. Nevertheless, these reports should pass unnoticed by the reported driver to avoid his/her potential reprisals. Information hiding techniques could be used to allow vehicles to transmit information covertly. In this work, two mechanisms for vehicle reporting are proposed based on two information hiding techniques— subliminal channels and steganography. The approach is to embed information into beacon messages either in the signature process (subliminal channel) or altering the least significant bits of selected sensorial fields (steganography). Results show that the proposal is computationally feasible for current vehicular devices and that it is possible to configure the system to operate in highways, secondary roads, and urban maps.

Subliminal Response Priming in Mixed Reality: The Ecological Validity of a Classic Paradigm of Perception

Subliminal stimuli can affect perception, decision-making, and action without being accessible to conscious awareness. Most evidence supporting this notion has been obtained in highly controlled laboratory conditions. Hence, its generalization to more realistic and ecologically valid contexts is unclear. Here, we investigate the impact of subliminal cues in an immersive navigation task using the so-called eXperience Induction Machine (XIM), a human accessible mixed-reality system. Subjects were asked to navigate through a maze at high speed. At irregular intervals, one group of subjects was exposed to subliminal aversive stimuli using the masking paradigm. We hypothesized that these stimuli would bias decision-making. Indeed, our results confirm this hypothesis and indicate that a subliminal channel of interaction exists between the user and the XIM. These results are relevant in our understanding of the bandwidth of communication that can be established between humans and their physical and social environment, thus opening up to new and powerful methods to interface humans and artefacts.

Performance Analysis of Transport Layer Basedhybrid Covert Channel Detection Engine

Computer network is unpredictable due to information warfareand is prone to various attacks. Such attacks on network compromiseson the most important attribute, the privacy. Most of such attacksare devised using special communication channel called Channel.The word Covert stands for hidden or nontransparent.Network Channel is concealed communication paths within legitimatenetwork communication that clearly violates security policies laiddown. Non-transparency in covert channel is also referred to as trapdoor.A trapdoor is unintended design within legitimate communication whosemotto is leak information. Subliminal channel, a variant of covert channelworks similarly as network covert channel except that trapdoor is setin cryptographic algorithm. A composition of covert channel with subliminalchannel is the Hybrid Channel. Hybrid covert channelis the homogeneous or heterogeneous mixture of two or more variantsof covert channel either active at same instance or at different instanceof time. Detecting such malicious channel activity plays a vital role inremoving threat to legitimate network.In this paper, we introduce new detection engine for hybrid covert channelin transport layer visualized in TCP and SSL. A setup made onexperimental test bed (DE-HCC9) in RD Lab of our department. Thepurpose of this study is to introduce few performance metrics to evaluatedetection engine and also to understand the multi-trapdoor natureof covert channel.

Toward a taxonomy of communications security models

Formal specifications, models and their accompanying proofs have long been promoted as setting the highest standard for program verification. But computer security remains threatened by covert channels, subliminal channels, side channels, fault injections, bypass, protocol attacks, and subversion despite rigorous application of formal methods. We advance the thesis that there exist several hierarchically ordered and adjacent sciences, notations, and security requirements analyses which must each be addressed to achieve comprehensive security. We support this thesis from a survey of relevant models of communications security. We argue that a taxonomy of security concerns consisting of levels called “Epochs” provides a comprehensive framework for identifying, locating, and analyzing security requirements and assumptions and gives sense to the effective use of formal methods.

Fair offline digital content transaction system

More and more customers are purchasing digital content through the Internet because it is both popular and convenient. However, there are lots of pirated editions of digital products and they have become more available and easier to obtain. Hence, proving who the legal owner of digital content has become an important issue. In this study, the authors want to preserve customer ownership; they propose an intact arbitration mechanism to solve the fairness transaction between the customer and the shop. The arbiter can make correct judgements without the customer's and the shop's private keys in the arbitration phase. In order to achieve the above objectives, the security of this protocol is based on three cryptographic techniques: the subliminal channel, one-way hash function and RSA cryptosystem. Our scheme not only protects a customer's legal ownership of digital content, but also achieves fair transaction, customer anonymity, owner tracing of E-cash and payment security.

Soundtrack Localisation

This paper focuses on the localisation and adaptation of one particular aspect of the computer game: the soundtrack. Sometimes bespoke, sometimes selected from commercial releases, it provides a background, supporting role in creating atmosphere and supporting the emotive state of the game space. But how often is the target market considered when selecting appropriate musical content? Is it possible to use this almost subliminal channel into the game player’s consciousness to increase his awareness of what is happening around him, and give him a feel for his character’s emotional and physical wellbeing? This paper presents a novel approach for transforming the soundtrack - via a system the author originally created for the purposes of capturing and recreating emotive content in music.

Two extensions of the ring signature scheme of Rivest–Shamir–Taumann

Two extensions of RST (Rivest, Shamir and Taumann) ring signature are proposed which keep the form of RST ring signature unchanged. One extension is to implement the verifiability property with which the real signer is able to prove that she actually signed the ring signature if she publishes her secret value. In contrast to the available verifiable ring signatures, this scheme is very simple, secure and efficient. In this scheme only the glue value of RST ring signature is replaced by the output of a hash function which takes as input a secret value and some signature parameters and the real signer is able to prove himself any times. The other extension is to construct an anonymous subliminal channel in RST ring signature so that the subliminal sender (the real signer) is able to keep herself subliminal anonymous to the subliminal receiver. The subliminal anonymity is implemented for the first time in this paper. In addition, if the sender wants to revoke the subliminal anonymity, she is able to use the first extension.

An extended matrix encoding algorithm for steganography of high embedding efficiency

F5 steganography is much different from most of LSB replacement or matching steganographic schemes, because matrix encoding is employed to increase embedding efficiency while reducing the number of necessary changes. By using this scheme, the hidden message inserted into carrier media imperceptibly can be transferred via a more secure subliminal channel. The embedding domain is the quantized DCT coefficients of JPEG image, which makes the scheme be immune to visual attack and statistical attack from the steganalyst. Based on this effective scheme, an extended matrix encoding algorithm is proposed to improve the performance further in this paper. By changing the hash function in matrix encoding and converting the coding mode, the embedding efficiency and embedding rate get increased to a large extent. Eventually, the experimental results demonstrate the extended algorithm is superior to the classic F5 steganography.