Digital image watermarking: its formal model, fundamental properties and possible attacks

While formal definitions and security proofs are well established in some fields like cryptography and steganography, they are not as evident in digital watermarking research. A systematic development of watermarking schemes is desirable, but at present their development is usually informal, ad hoc, and omits the complete realization of application scenarios. This practice not only hinders the choice and use of a suitable scheme for a watermarking application, but also leads to debate about the state-of-the-art for different watermarking applications. With a view to the systematic development of watermarking schemes, we present a formal generic model for digital image watermarking. Considering possible inputs, outputs, and component functions, the initial construction of a basic watermarking model is developed further to incorporate the use of keys. On the basis of our proposed model, fundamental watermarking properties are defined and their importance exemplified for different image applications. We also define a set of possible attacks using our model showing different winning scenarios depending on the adversary capabilities. It is envisaged that with a proper consideration of watermarking properties and adversary actions in different image applications, use of the proposed model would allow a unified treatment of all practically meaningful variants of watermarking schemes

(In)Security of an Efficient Fingerprinting Scheme with Symmetric and Commutative Encryption of IWDW 2005

We analyze the security of a fingerprinting scheme proposed at IWDW 2005. We show two results, namely that this scheme (1) does riot provide seller security: a dishonest buyer can repudiate the fact that, he redistributed a content, and (2) does riot, provide buyer security: a buyer can be framed by a malicious seller

Secure fingerprinting on sound foundations

The rapid development and the advancement of digital technologies open a variety of opportunities to consumers and content providers for using and trading digital goods. In this context, particularly the Internet has gained a major ground as a worldwiede platform for exchanging and distributing digital goods. Beside all its possibilities and advantages digital technology can be misuesd to breach copyright regulations: unauthorized use and illegal distribution of intellectual property cause authors and content providers considerable loss. Protections of intellectual property has therefore become one of the major challenges of our information society. Fingerprinting is a key technology in copyright protection of intellectual property. Its goal is to deter people from copyright violation by allowing to provably identify the source of illegally copied and redistributed content. As one of its focuses, this thesis considers the design and construction of various fingerprinting schemes and presents the first explicit, secure and reasonably efficient construction for a fingerprinting scheme which fulfills advanced security requirements such as collusion-tolerance, asymmetry, anonymity and direct non-repudiation. Crucial for the security of such s is a careful study of the underlying cryptographic assumptions. In case of the fingerprinting scheme presented here, these are mainly assumptions related to discrete logarithms. The study and analysis of these assumptions is a further focus of this thesis. Based on the first thorough classification of assumptions related to discrete logarithms, this thesis gives novel insights into the relations between these assumptions. In particular, depending on the underlying probability space we present new reuslts on the reducibility between some of these assumptions as well as on their reduction efficency.Die Fortschritte im Bereich der Digitaltechnologien bieten Konsumenten, Urhebern und Anbietern große Potentiale für innovative Geschäftsmodelle zum Handel mit digitalen Gütern und zu deren Nutzung. Das Internet stellt hierbei eine interessante Möglichkeit zum Austausch und zur Verbreitung digitaler Güter dar. Neben vielen Vorteilen kann die Digitaltechnik jedoch auch missbräuchlich eingesetzt werden, wie beispielsweise zur Verletzung von Urheberrechten durch illegale Nutzung und Verbreitung von Inhalten, wodurch involvierten Parteien erhebliche Schäden entstehen können. Der Schutz des geistigen Eigentums hat sich deshalb zu einer der besonderen Herausforderungen unseres Digitalzeitalters entwickelt. Fingerprinting ist eine Schlüsseltechnologie zum Urheberschutz. Sie hat das Ziel, vor illegaler Vervielfältigung und Verteilung digitaler Werke abzuschrecken, indem sie die Identifikation eines Betrügers und das Nachweisen seines Fehlverhaltens ermöglicht. Diese Dissertation liefert als eines ihrer Ergebnisse die erste explizite, sichere und effiziente Konstruktion, welche die Berücksichtigung besonders fortgeschrittener Sicherheitseigenschaften wie Kollusionstoleranz, Asymmetrie, Anonymität und direkte Unabstreitbarkeit erlaubt. Entscheidend für die Sicherheit kryptographischer Systeme ist die präzise Analyse der ihnen zugrunde liegenden kryptographischen Annahmen. Den im Rahmen dieser Dissertation konstruierten Fingerprintingsystemen liegen hauptsächlich kryptographische Annahmen zugrunde, welche auf diskreten Logarithmen basieren. Die Untersuchung dieser Annahmen stellt einen weiteren Schwerpunkt dieser Dissertation dar. Basierend auf einer hier erstmals in der Literatur vorgenommenen Klassifikation dieser Annahmen werden neue und weitreichende Kenntnisse über deren Zusammenhänge gewonnen. Insbesondere werden, in Abhängigkeit von dem zugrunde liegenden Wahrscheinlichkeitsraum, neue Resultate hinsichtlich der Reduzierbarkeit dieser Annahmen und ihrer Reduktionseffizienz erzielt

Framework for privacy-aware content distribution in peer-to- peer networks with copyright protection

The use of peer-to-peer (P2P) networks for multimedia distribution has spread out globally in recent years. This mass popularity is primarily driven by the efficient distribution of content, also giving rise to piracy and copyright infringement as well as privacy concerns. An end user (buyer) of a P2P content distribution system does not want to reveal his/her identity during a transaction with a content owner (merchant), whereas the merchant does not want the buyer to further redistribute the content illegally. Therefore, there is a strong need for content distribution mechanisms over P2P networks that do not pose security and privacy threats to copyright holders and end users, respectively. However, the current systems being developed to provide copyright and privacy protection to merchants and end users employ cryptographic mechanisms, which incur high computational and communication costs, making these systems impractical for the distribution of big files, such as music albums or movies.El uso de soluciones de igual a igual (peer-to-peer, P2P) para la distribución multimedia se ha extendido mundialmente en los últimos años. La amplia popularidad de este paradigma se debe, principalmente, a la distribución eficiente de los contenidos, pero también da lugar a la piratería, a la violación del copyright y a problemas de privacidad. Un usuario final (comprador) de un sistema de distribución de contenidos P2P no quiere revelar su identidad durante una transacción con un propietario de contenidos (comerciante), mientras que el comerciante no quiere que el comprador pueda redistribuir ilegalmente el contenido más adelante. Por lo tanto, existe una fuerte necesidad de mecanismos de distribución de contenidos por medio de redes P2P que no supongan un riesgo de seguridad y privacidad a los titulares de derechos y los usuarios finales, respectivamente. Sin embargo, los sistemas actuales que se desarrollan con el propósito de proteger el copyright y la privacidad de los comerciantes y los usuarios finales emplean mecanismos de cifrado que implican unas cargas computacionales y de comunicaciones muy elevadas que convierten a estos sistemas en poco prácticos para distribuir archivos de gran tamaño, tales como álbumes de música o películas.L'ús de solucions d'igual a igual (peer-to-peer, P2P) per a la distribució multimèdia s'ha estès mundialment els darrers anys. L'àmplia popularitat d'aquest paradigma es deu, principalment, a la distribució eficient dels continguts, però també dóna lloc a la pirateria, a la violació del copyright i a problemes de privadesa. Un usuari final (comprador) d'un sistema de distribució de continguts P2P no vol revelar la seva identitat durant una transacció amb un propietari de continguts (comerciant), mentre que el comerciant no vol que el comprador pugui redistribuir il·legalment el contingut més endavant. Per tant, hi ha una gran necessitat de mecanismes de distribució de continguts per mitjà de xarxes P2P que no comportin un risc de seguretat i privadesa als titulars de drets i els usuaris finals, respectivament. Tanmateix, els sistemes actuals que es desenvolupen amb el propòsit de protegir el copyright i la privadesa dels comerciants i els usuaris finals fan servir mecanismes d'encriptació que impliquen unes càrregues computacionals i de comunicacions molt elevades que fan aquests sistemes poc pràctics per a distribuir arxius de grans dimensions, com ara àlbums de música o pel·lícules

Kleptography and steganography in blockchains

Despite its vast proliferation, the blockchain technology is still evolving, and witnesses continuous technical innovations to address its numerous unresolved issues. An example of these issues is the excessive electrical power consumed by some consensus protocols. Besides, although various media reports have highlighted the existence of objectionable content in blockchains, this topic has not received sufficient research. Hence, this work investigates the threat and deterrence of arbitrary-content insertion in public blockchains, which poses a legal, moral, and technical challenge. In particular, the overall aim of this work is to thoroughly study the risk of manipulating the implementation of randomized cryptographic primitives in public blockchains to mount kleptographic attacks, establish steganographic communication, and store arbitrary content. As part of our study, we present three new kleptographic attacks on two of the most commonly used digital signatures: ring signature and ECDSA. We also demonstrate our kleptographic attacks on two real cryptocurrencies: Bytecoin and Monero. Moreover, we illustrate the plausibility of hijacking public blockchains to establish steganographic channels. Particularly, we design, implement, and evaluate the first blockchain-based broadcast communication tool on top of a real-world cryptocurrency. Furthermore, we explain the detrimental consequences of kleptography and steganography on the users and the future of the blockchain technology. Namely, we show that kleptography can be used to surreptitiously steal the users' secret signing keys, which are the most valuable and guarded secret in public blockchains. After losing their keys, users of cryptocurrencies will inevitably lose their funds. In addition, we clarify that steganography can be used to establish subliminal communication and secretly store arbitrary content in public blockchains, which turns them into cheap cyberlockers. Consequently, the participation in such blockchains, which are known to store unethical content, can be criminalized, hindering the future adoption of blockchains. After discussing the adverse effects of kleptographic and steganographic attacks on blockchains, we survey all of the existing techniques that can defend against these attacks. Finally, due to the shortcomings of the available techniques, we propose four countermeasures that ensure kleptography and steganography-resistant public blockchains. Our countermeasures include two new cryptographic primitives and a generic steganographyresistant blockchain framework (SRBF). This framework presents a universal solution that deters steganography and practically achieves the right to be forgotten (RtbF) in blockchains, which represents a regulatory challenge for current immutable blockchains

NEW SECURE SOLUTIONS FOR PRIVACY AND ACCESS CONTROL IN HEALTH INFORMATION EXCHANGE

In the current digital age, almost every healthcare organization (HCO) has moved from storing patient health records on paper to storing them electronically. Health Information Exchange (HIE) is the ability to share (or transfer) patients’ health information between different HCOs while maintaining national security standards like the Health Insurance Portability and Accountability Act (HIPAA) of 1996. Over the past few years, research has been conducted to develop privacy and access control frameworks for HIE systems. The goal of this dissertation is to address the privacy and access control concerns by building practical and efficient HIE frameworks to secure the sharing of patients’ health information. The first solution allows secure HIE among different healthcare providers while focusing primarily on the privacy of patients’ information. It allows patients to authorize a certain type of health information to be retrieved, which helps prevent any unintentional leakage of information. The privacy solution also provides healthcare providers with the capability of mutual authentication and patient authentication. It also ensures the integrity and auditability of health information being exchanged. The security and performance study for the first protocol shows that it is efficient for the purpose of HIE and offers a high level of security for such exchanges. The second framework presents a new cloud-based protocol for access control to facilitate HIE across different HCOs, employing a trapdoor hash-based proxy signature in a novel manner to enable secure (authenticated and authorized) on-demand access to patient records. The proposed proxy signature-based scheme provides an explicit mechanism for patients to authorize the sharing of specific medical information with specific HCOs, which helps prevent any undesired or unintentional leakage of health information. The scheme also ensures that such authorizations are authentic with respect to both the HCOs and the patient. Moreover, the use of proxy signatures simplifies security auditing and the ability to obtain support for investigations by providing non-repudiation. Formal definitions, security specifications, and a detailed theoretical analysis, including correctness, security, and performance of both frameworks are provided which demonstrate the improvements upon other existing HIE systems

Security and trust in cloud computing and IoT through applying obfuscation, diversification, and trusted computing technologies

Cloud computing and Internet of Things (IoT) are very widely spread and commonly used technologies nowadays. The advanced services offered by cloud computing have made it a highly demanded technology. Enterprises and businesses are more and more relying on the cloud to deliver services to their customers. The prevalent use of cloud means that more data is stored outside the organization’s premises, which raises concerns about the security and privacy of the stored and processed data. This highlights the significance of effective security practices to secure the cloud infrastructure. The number of IoT devices is growing rapidly and the technology is being employed in a wide range of sectors including smart healthcare, industry automation, and smart environments. These devices collect and exchange a great deal of information, some of which may contain critical and personal data of the users of the device. Hence, it is highly significant to protect the collected and shared data over the network; notwithstanding, the studies signify that attacks on these devices are increasing, while a high percentage of IoT devices lack proper security measures to protect the devices, the data, and the privacy of the users. In this dissertation, we study the security of cloud computing and IoT and propose software-based security approaches supported by the hardware-based technologies to provide robust measures for enhancing the security of these environments. To achieve this goal, we use obfuscation and diversification as the potential software security techniques. Code obfuscation protects the software from malicious reverse engineering and diversification mitigates the risk of large-scale exploits. We study trusted computing and Trusted Execution Environments (TEE) as the hardware-based security solutions. Trusted Platform Module (TPM) provides security and trust through a hardware root of trust, and assures the integrity of a platform. We also study Intel SGX which is a TEE solution that guarantees the integrity and confidentiality of the code and data loaded onto its protected container, enclave. More precisely, through obfuscation and diversification of the operating systems and APIs of the IoT devices, we secure them at the application level, and by obfuscation and diversification of the communication protocols, we protect the communication of data between them at the network level. For securing the cloud computing, we employ obfuscation and diversification techniques for securing the cloud computing software at the client-side. For an enhanced level of security, we employ hardware-based security solutions, TPM and SGX. These solutions, in addition to security, ensure layered trust in various layers from hardware to the application. As the result of this PhD research, this dissertation addresses a number of security risks targeting IoT and cloud computing through the delivered publications and presents a brief outlook on the future research directions.Pilvilaskenta ja esineiden internet ovat nykyään hyvin tavallisia ja laajasti sovellettuja tekniikkoja. Pilvilaskennan pitkälle kehittyneet palvelut ovat tehneet siitä hyvin kysytyn teknologian. Yritykset enenevässä määrin nojaavat pilviteknologiaan toteuttaessaan palveluita asiakkailleen. Vallitsevassa pilviteknologian soveltamistilanteessa yritykset ulkoistavat tietojensa käsittelyä yrityksen ulkopuolelle, minkä voidaan nähdä nostavan esiin huolia taltioitavan ja käsiteltävän tiedon turvallisuudesta ja yksityisyydestä. Tämä korostaa tehokkaiden turvallisuusratkaisujen merkitystä osana pilvi-infrastruktuurin turvaamista. Esineiden internet -laitteiden lukumäärä on nopeasti kasvanut. Teknologiana sitä sovelletaan laajasti monilla sektoreilla, kuten älykkäässä terveydenhuollossa, teollisuusautomaatiossa ja älytiloissa. Sellaiset laitteet keräävät ja välittävät suuria määriä informaatiota, joka voi sisältää laitteiden käyttäjien kannalta kriittistä ja yksityistä tietoa. Tästä syystä johtuen on erittäin merkityksellistä suojata verkon yli kerättävää ja jaettavaa tietoa. Monet tutkimukset osoittavat esineiden internet -laitteisiin kohdistuvien tietoturvahyökkäysten määrän olevan nousussa, ja samaan aikaan suuri osuus näistä laitteista ei omaa kunnollisia teknisiä ominaisuuksia itse laitteiden tai niiden käyttäjien yksityisen tiedon suojaamiseksi. Tässä väitöskirjassa tutkitaan pilvilaskennan sekä esineiden internetin tietoturvaa ja esitetään ohjelmistopohjaisia tietoturvalähestymistapoja turvautumalla osittain laitteistopohjaisiin teknologioihin. Esitetyt lähestymistavat tarjoavat vankkoja keinoja tietoturvallisuuden kohentamiseksi näissä konteksteissa. Tämän saavuttamiseksi työssä sovelletaan obfuskaatiota ja diversifiointia potentiaalisiana ohjelmistopohjaisina tietoturvatekniikkoina. Suoritettavan koodin obfuskointi suojaa pahantahtoiselta ohjelmiston takaisinmallinnukselta ja diversifiointi torjuu tietoturva-aukkojen laaja-alaisen hyödyntämisen riskiä. Väitöskirjatyössä tutkitaan luotettua laskentaa ja luotettavan laskennan suoritusalustoja laitteistopohjaisina tietoturvaratkaisuina. TPM (Trusted Platform Module) tarjoaa turvallisuutta ja luottamuksellisuutta rakentuen laitteistopohjaiseen luottamukseen. Pyrkimyksenä on taata suoritusalustan eheys. Työssä tutkitaan myös Intel SGX:ää yhtenä luotettavan suorituksen suoritusalustana, joka takaa suoritettavan koodin ja datan eheyden sekä luottamuksellisuuden pohjautuen suojatun säiliön, saarekkeen, tekniseen toteutukseen. Tarkemmin ilmaistuna työssä turvataan käyttöjärjestelmä- ja sovellusrajapintatasojen obfuskaation ja diversifioinnin kautta esineiden internet -laitteiden ohjelmistokerrosta. Soveltamalla samoja tekniikoita protokollakerrokseen, työssä suojataan laitteiden välistä tiedonvaihtoa verkkotasolla. Pilvilaskennan turvaamiseksi työssä sovelletaan obfuskaatio ja diversifiointitekniikoita asiakaspuolen ohjelmistoratkaisuihin. Vankemman tietoturvallisuuden saavuttamiseksi työssä hyödynnetään laitteistopohjaisia TPM- ja SGX-ratkaisuja. Tietoturvallisuuden lisäksi nämä ratkaisut tarjoavat monikerroksisen luottamuksen rakentuen laitteistotasolta ohjelmistokerrokseen asti. Tämän väitöskirjatutkimustyön tuloksena, osajulkaisuiden kautta, vastataan moniin esineiden internet -laitteisiin ja pilvilaskentaan kohdistuviin tietoturvauhkiin. Työssä esitetään myös näkemyksiä jatkotutkimusaiheista