A Secure Traitor Tracing Scheme against Key Exposure

Copyright protection is a major issue in distributing digital content. On the other hand, improvements to usability are sought by content users. In this paper, we propose a secure {\it traitor tracing scheme against key exposure (TTaKE)} which contains the properties of both a traitor tracing scheme and a forward secure public key cryptosystem. Its structure fits current digital broadcasting systems and it may be useful in preventing traitors from making illegal decoders and in minimizing the damage from accidental key exposure. It can improve usability through these properties.Comment: 5 pages, IEEE International Symposium on Information Theory 2005 (ISIT 2005

Continuous Group Key Agreement with Flexible Authorization and Its Applications

Secure messaging (SM) protocols allow users to communicate securely over an untrusted infrastructure. The IETF currently works on the standardization of secure group messaging (SGM), which is SM done by a group of two or more people. Alwen et al. formally defined the key agreement protocol used in SGM as continuous group key agreement (CGKA) at CRYPTO 2020. In their CGKA protocol, all of the group members have the same rights and a trusted third party is needed. On the contrary, some SGM applications may have a user in the group who has the role of an administrator. When the administrator as the group manager (GM) is distinguished from other group members, i.e., in a one-to-many setting, it would be better for the GM and the other group members to have different authorities. We achieve this flexible autho-rization by incorporating a ratcheting digital signature scheme (Cremers et al. at USENIX Security 2021) into the existing CGKA protocol and demonstrate that such a simple modification allows us to provide flexible authorization. This one-to-many setting may be reminiscent of a multi-cast key agreement protocol proposed by Bienstock et al. at CT-RSA 2022, where GM has the role of adding and removing group members. Although the role of the GM is fixed in advance in the Bienstock et al. protocol, the GM can flexibly set the role depending on the application in our protocol. On the other hand, in Alwen et al.’s CGKA protocol, an external public key infrastructure (PKI) functionality as a trusted third party manages the confidential information of users, and the PKI can read all messages until all users update their own keys. In contrast, the GM in our protocol has the same role as the PKI functionality in the group, so no third party outside the group handles confidential informa-tion of users and thus no one except group members can read messages regardless of key updates. Our proposed protocol is useful in the creation of new applications such as broadcasting services

Efficient and Secure Data Sharing Using Attribute-based Cryptography

La crescita incontrollata di dati prodotti da molte sorgenti, eterogenee e di- namiche, spinge molti possessori di tali dati a immagazzinarli su server nel cloud, anche al fine di condividerli con terze parti. La condivisione di dati su server (possibilmente) non fidati fonte di importanti e non banali questioni riguardanti sicurezza, privacy, confidenzialit e controllo degli accessi. Al fine di prevenire accessi incontrollati ai dati, una tipica soluzione consiste nel cifrare i dati stessi. Seguendo tale strada, la progettazione e la realizzazione di politiche di accesso ai dati cifrati da parte di terze parti (che possono avere differenti diritti sui dati stessi) un compito complesso, che impone la presenza di un controllore fidato delle politiche. Una possibile soluzione l\u2019impiego di un meccanismo per il controllo degli accessi basato su schemi di cifratura attribute-base (ABE ), che permette al possessore dei dati di cifrare i dati in funzione delle politiche di accesso dei dati stessi. Di contro, l\u2019adozione di tali meccanismi di controllo degli accessi presentano due problemi (i) privacy debole: le politiche di accesso sono pubbliche e (ii) inefficienza: le politiche di accesso sono statiche e una loro modifica richiede la ricifratura (o la cifratura multipla) di tutti i dati. Al fine di porre rimedio a tali problemi, il lavoro proposto in questa tesi prende in con- siderazione un particolare schema di cifratura attribute-based, chiamato inner product encryption (IPE, che gode della propriet attribute-hiding e pertanto riesce a proteggere la privatezza delle politiche di accesso) e lo combina con le tecniche di proxy re-encryption, che introducono una maggiore flessibilit ed efficienza. La prima parte di questa tesi discute l\u2019adeguatezza dell\u2019introduzione di un meccanismo di controllo degli accessi fondato su schema basato su inner product e proxy re-encryption (IPPRE ) al fine di garantire la condivisione sicura di dati immagazzinati su cloud server non fidati. Pi specificamente, proponiamo due proponiamo due versioni di IPE : in prima istanza, presentiamo una versione es- tesa con proxy re-encryption di un noto schema basato su inner product [1]. In seguito, usiamo tale schema in uno scenario in cui vengono raccolti e gestiti dati medici. In tale scenario, una volta che i dati sono stati raccolti, le politiche di ac- cesso possono variare al variare delle necessit dei diversi staff medici. Lo schema proposto delega il compito della ricifratura dei dati a un server proxy parzial- mente fidato, che pu trasformare la cifratura dei dati (che dipende da una polit- ica di accesso) in un\u2019altra cifratura (che dipende da un\u2019altra politica di accesso) senza per questo avere accesso ai dati in chiaro o alla chiave segreta utilizzata dal possessore dei dati. In tal modo, il possessore di una chiave di decifratura corrispondente alla seconda politica di accesso pu accedere ai dati senza intera- gire con il possessore dei dati (richiedendo cio una chiave di decifratura associata alla propria politica di accesso). Presentiamo un\u2019analisi relativa alle prestazioni di tale schema implementato su curve ellittiche appartenenti alle classi SS, MNT e BN e otteniamo incoraggianti risultati sperimentali. Dimostriamo inoltre che lo schema proposto sicuro contro attacchi chosen plaintext sotto la nota ipotesi DLIN. In seconda istanza, presentiamo una versione ottimizzata dello schema proposto in precedenza (E-IPPRE ), basata su un ben noto schema basato suinner product, proposto da Kim [2]. Lo schema E-IPPRE proposto richiede un numero costante di operazioni di calcolo di pairing e ci garantisce che gli oggetti prodotti dall esecuzione dello schema (chiavi di decifratura, chiavi pubbliche e le cifrature stesse) sono di piccole rispetto ai parametri di sicurezza e sono efficientemente calcolabili. Testiamo sperimentalmente l\u2019efficienza dello schema proposto e lo proviamo (selettivamente nei confronti degli attributi) sicuro nei confronti di attacchi chosen plaintext sotto la nota ipotesi BDH. In altri termini, lo schema proposto non rivela alcuna informazione riguardante le politiche di accesso. La seconda parte di questa tesi presenta uno schema crittografico per la condivisione sicura dei dati basato su crittografia attribute-based e adatto per scenari basati su IoT. Come noto, il problema principale in tale ambito riguarda le limitate risorse computazionali dei device IoT coinvolti. A tal proposito, proponiamo uno schema che combina la flessibilit di E-IPPRE con l\u2019efficienza di uno schema di cifratura simmetrico quale AES, ottenendo uno schema di cifratura basato su inner product, proxy-based leggero (L-IPPRE ). I risultati sperimentali confermano l\u2019adeguatezza di tale schema in scenari IoT.Riferimenti [1] Jong Hwan Park. Inner-product encryption under standard assumptions. Des. Codes Cryptography, 58(3):235\u2013257, March 2011. [2] Intae Kim, Seong Oun Hwang, Jong Hwan Park, and Chanil Park. An effi- cient predicate encryption with constant pairing computations and minimum costs. IEEE Trans. Comput., 65(10):2947\u20132958, October 2016.With the ever-growing production of data coming from multiple, scattered, and highly dynamical sources, many providers are motivated to upload their data to the cloud servers and share them with other persons for different purposes. However, storing data on untrusted cloud servers imposes serious concerns in terms of security, privacy, data confidentiality, and access control. In order to prevent privacy and security breaches, it is vital that data is encrypted first before it is outsourced to the cloud. However, designing access control mod- els that enable different users to have various access rights to the shared data is the main challenge. To tackle this issue, a possible solution is to employ a cryptographic-based data access control mechanism such as attribute-based encryption (ABE ) scheme, which enables a data owner to take full control over data access. However, access control mechanisms based on ABE raise two chal- lenges: (i) weak privacy: they do not conceal the attributes associated with the ciphertexts, and therefore they do not satisfy attribute-hiding security, and (ii) inefficiency: they do not support efficient access policy change when data is required to be shared among multiple users with different access policies. To address these issues, this thesis studies and enhances inner-product encryption (IPE ), a type of public-key cryptosystem, which supports the attribute-hiding property as well as the flexible fine-grained access control based payload-hiding property, and combines it with an advanced cryptographic technique known as proxy re-encryption (PRE ). The first part of this thesis discusses the necessity of applying the inner- product proxy re-encryption (IPPRE ) scheme to guarantee secure data sharing on untrusted cloud servers. More specifically, we propose two extended schemes of IPE : in the first extended scheme, we propose an inner-product proxy re- encryption (IPPRE ) protocol derived from a well-known inner-product encryp- tion scheme [1]. We deploy this technique in the healthcare scenario where data, collected by medical devices according to some access policy, has to be changed afterwards for sharing with other medical staffs. The proposed scheme delegates the re-encryption capability to a semi-trusted proxy who can transform a dele- gator\u2019s ciphertext associated with an attribute vector to a new ciphertext associ- ated with delegatee\u2019s attribute vector set, without knowing the underlying data and private key. Our proposed policy updating scheme enables the delegatee to decrypt the shared data with its own key without requesting a new decryption key. We analyze the proposed protocol in terms of its performance on three dif- ferent types of elliptic curves such as the SS curve, the MNT curve, and the BN curve, respectively. Hereby, we achieve some encouraging experimental results. We show that our scheme is adaptive attribute-secure against chosen-plaintext under standard Decisional Linear (D-Linear ) assumption. To improve the per- formance of this scheme in terms of storage, communication, and computation costs, we propose an efficient inner-product proxy re-encryption (E-IPPRE ) scheme using the transformation of Kim\u2019s inner-product encryption method [2]. The proposed E-IPPRE scheme requires constant pairing operations for its al- gorithms and ensures a short size of the public key, private key, and ciphertext,making it the most efficient and practical compared to state of the art schemes in terms of computation and communication overhead. We experimentally as- sess the efficiency of our protocol and show that it is selective attribute-secure against chosen-plaintext attacks in the standard model under Asymmetric De- cisional Bilinear Diffie-Hellman assumption. Specifically, our proposed schemes do not reveal any information about the data owner\u2019s access policy to not only the untrusted servers (e.g, cloud and proxy) but also to the other users. The second part of this thesis presents a new lightweight secure data sharing scheme based on attribute-based cryptography for a specific IoT -based health- care application. To achieve secure data sharing on IoT devices while preserving data confidentiality, the IoT devices encrypt data before it is outsourced to the cloud and authorized users, who have corresponding decryption keys, can ac- cess the data. The main challenge, in this case, is on the one hand that IoT devices are resource-constrained in terms of energy, CPU, and memory. On the other hand, the existing public-key encryption mechanisms (e.g., ABE ) require expensive computation. We address this issue by combining the flexibility and expressiveness of the proposed E-IPPRE scheme with the efficiency of symmet- ric key encryption technique (AES ) and propose a light inner-product proxy re-encryption (L-IPPRE ) scheme to guarantee secure data sharing between dif- ferent entities in the IoT environment. The experimental results confirm that the proposed L-IPPRE scheme is suitable for resource-constrained IoT scenar- ios.References [1] Jong Hwan Park. Inner-product encryption under standard assumptions. Des. Codes Cryptography, 58(3):235\u2013257, March 2011. [2] Intae Kim, Seong Oun Hwang, Jong Hwan Park, and Chanil Park. An effi- cient predicate encryption with constant pairing computations and minimum costs. IEEE Trans. Comput., 65(10):2947\u20132958, October 2016

Data and the city – accessibility and openness. a cybersalon paper on open data

This paper showcases examples of bottom–up open data and smart city applications and identifies lessons for future such efforts. Examples include Changify, a neighbourhood-based platform for residents, businesses, and companies; Open Sensors, which provides APIs to help businesses, startups, and individuals develop applications for the Internet of Things; and Cybersalon’s Hackney Treasures. a location-based mobile app that uses Wikipedia entries geolocated in Hackney borough to map notable local residents. Other experiments with sensors and open data by Cybersalon members include Ilze Black and Nanda Khaorapapong's The Breather, a "breathing" balloon that uses high-end, sophisticated sensors to make air quality visible; and James Moulding's AirPublic, which measures pollution levels. Based on Cybersalon's experience to date, getting data to the people is difficult, circuitous, and slow, requiring an intricate process of leadership, public relations, and perseverance. Although there are myriad tools and initiatives, there is no one solution for the actual transfer of that data

Australian migrant heritage in south China : the legacy of diaspora-funded schools in twentieth century Zhongshan

This interdisciplinary study addresses a problem of intellectual concern at the intersection of the scholarly fields of heritage studies and migration history: How to recognise and manage the heritage of a shared past beyond the boundaries of the nation-state? Existing research and conservation practice on sites of migrant heritage in Australia conventionally considers events and places related to the immigrant experience after they arrive in Australia, but not their continuing links to migrant places of origin overseas. An exception to this is the China–Australia Heritage Corridor project—an Australian Research Council-funded Discovery Project initiated by researchers at the Institute for Culture and Society at Western Sydney University to document the diasporic dimension of Chinese migrant heritage to Australia in the nineteenth and twentieth centuries. Under the umbrella of the China–Australia Heritage Corridor project, this doctoral thesis specifically explores the social and architectural dimension of the Chinese diaspora’s educational philanthropy in the period from the early twentieth century until the present. It helps reveal how Chinese migration to Australia ultimately resulted in the socio-material transformation of the native home of migrants in the Pearl River Delta of China’s Guangdong Province, specifically in relation to the construction and operation of modern schools there. This thesis presents a dual—qiaoxiang and diaspora—perspective that disrupts the conventional understanding of migrant heritage as defined by the nation-state. The study is the first of its kind to examine how the Chinese diaspora relates to the material heritage of the diaspora-funded school setting in China. Diaspora-funded schools were unique socio-material assemblages that first emerged in southern China in the early twentieth century. This thesis reveals how the modern school shaped a new way of life and future for the qiaoxiang. The socio-material legacies of the diaspora-funded school buildings are a testimony to the generosity of the donors, but the schools may also become a burden for donors and their descendants, requiring maintenance and continuous improvement. Since the 1980s, Chinese migrants in Australia (and their descendants) continued the tradition of erecting new schools and renovating old ones as a way to contribute to the qiaoxiang’s future. But this second wave of construction only lasted until the turn of the twentieth-first century, after which China no longer depended on the diaspora as a funding source for schools. The thesis concludes that Chinese-Australian migrant heritage in China remains relevant to both China and Australia. It testifies to the history of their mutual entanglement and place-based attachment, as well as improving intergenerational relationships. It also has potential to strengthen the transnational ties established by the history of diaspora philanthropy

Battles with Words: Literate and Linguistic Resistance in Multi-Ethnic U.S. Literature and Everyday Life

Battles with Words analyzes the role of multi-ethnic U.S. literature as an alternative form of cultural production which critiques and challenges U.S. linguistic and literate hegemony and homogeneity. The texts comprising this field continually emphasize the ways in which words, through language and literacy, become tools of power and action used by the ethnically marginalized to negotiate everyday advantages for themselves and challenge the linguistic and cultural domination of Anglo America. Through their critiques of the culture of English-only monolingualism that has continued to dominate the national landscape of the U.S. throughout the twentieth and twenty-first centuries, these authors indicate their concern with the ways language intersects with and impacts literature, as well as their interest in using literature to explore and critique the relationship between language, literacy, race, ethnicity, and citizenship in the U.S. Using seven contemporary multi-ethnic U.S. novels, I examine how these novels portray language and literacy as weapons of the dominant which maintain and reproduce racist, classist systems of power and bureaucracy and as tools for those who are positioned as ethnically, linguistically, and nationally unauthorized, subjugated, and illegitimate to resist their subordination and disenfranchisement. By examining these works through a rhetorical lens, my analyses attempt to elucidate what is (un)said, (un)speakable, and (un)recorded when subordinates confront authorities in various public and private contexts including classrooms, social services offices, immigration stations, neighborhoods, and homes. The high-stakes literate and linguistic exchanges these works portray offer a multitude of perspectives from which to consider the seemingly mundane, ordinary ways in which language and literacy are used by the marginalized and the powerful as they negotiate various everyday contexts and encounters. While these novels reveal the many problematic uses of literacy and language in power struggles in the U.S., especially as they relate to race, ethnicity, and citizenship, they also suggest alternative ways that language and literacy might be used less hierarchically and more democratically in everyday life, offering models for transforming bureaucratic, institutional, and social encounters. These alternative models should interest not only literary scholars, but also those in the fields of composition, pedagogy, language, literacy and education