What a lovely hat

Dynamic searchable encryption (DSE) with forward and backward privacy reduces leakages in early-stage schemes. Security enhancement comes with a price -- maintaining updatable keyword-wise state information. State information, if stored locally, incurs significant client-side storage overhead for keyword-rich datasets, potentially hindering real-world deployments. We propose DISCO, a simple and efficient framework for designing DSE schemes using constant client state. DISCO combines...

Boolean Searchable Symmetric Encryption (SSE) enables secure outsourcing of databases to an untrusted server in encrypted form and allows the client to execute secure Boolean queries involving multiple keywords. The leakage of keyword pair result pattern (KPRP) in a Boolean search poses a significant threat, which reveals the intersection of documents containing any two keywords involved in a search and can be exploited by attackers to recover plaintext information about searched keywords...

Searchable Symmetric Encryption (SSE) has opened up an attractive avenue for privacy-preserved processing of outsourced data on the untrusted cloud infrastructure. SSE aims to support efficient Boolean query processing with optimal storage and search overhead over large real databases. However, current constructions in the literature lack the support for multi-client search and dynamic updates to the encrypted databases, which are essential requirements for the widespread deployment of SSE...

In differential-like attacks, the process typically involves extending a distinguisher forward and backward with probability 1 for some rounds and recovering the key involved in the extended part. Particularly in rectangle attacks, a holistic key recovery strategy can be employed to yield the most efficient attacks tailored to a given distinguisher. In this paper, we treat the distinguisher and the extended part as an integrated entity and give a one-step framework for finding rectangle...

Fully Homomorphic encryption allows the evaluation of any circuits over encrypted data while preserving the privacy of the data. However, without any additional properties, no guarantee is provided for the privacy of the circuits which are evaluated. A sanitization algorithm allows to destroy all previous information about how a ciphertext was obtained, ensuring that the circuit which was evaluated remains secret. In this paper, we present two techniques to randomize RLWE ciphertexts, and...

We study the problem of multi-user dynamic searchable symmetric encryption (DMUSSE) where a data owner stores its encrypted documents on an untrusted remote server and wishes to selectively allow multiple users to access them by issuing keyword search queries. Specifically, we consider the case where some of the users may be corrupted and colluding with the server to extract additional information about the dataset (beyond what they have access to). We provide the first formal security...

We focus on the problem of Dynamic Searchable Encryption (DSE) with efficient (optimal/quasi-optimal) search in the presence of deletions. Towards that end, we first propose $\mathsf{OSSE}$, the first DSE scheme that can achieve asymptotically optimal search time, linear to the result size and independent of any prior deletions, improving the previous state of the art by a multiplicative logarithmic factor. We then propose our second scheme $\mathsf{LLSE}$, that achieves a sublogarithmic...

Elliptic Curve Cryptography (ECC) has been popularly used in RFID authentication protocols to efficiently overcome many security and privacy issues. Even if the strong cryptography primitives of ECC are utilised in the authentication protocols, the schemes are alas far from providing security and privacy properties as desired level. In this paper, we analyze four up-to-minute ECC based RFID authentication schemes proposed by Gasbi et al., Benssalah et al., Kumar et al., and Agrahari and...

End-to-end encryption provides strong privacy protections to billions of people, but it also complicates efforts to moderate content that can seriously harm people. To address this concern, Tyagi et al. [CRYPTO 2019] introduced the concept of asymmetric message franking (AMF), which allows people to report abusive content to a moderator, while otherwise retaining end-to-end privacy by default and even compatibility with anonymous communication systems like Signal’s sealed sender. In this...

Recent developments in the field of Dynamic Searchable Symmetric Encryption (DSSE) with forward and backward privacy have attracted much attention from both research and industrial communities. However, most forward and backward private DSSE schemes support single keyword queries only, which impedes its prevalence in practice. Until recently, Patranabis et al. (NDSS 2021) introduced a forward and backward private DSSE for conjunctive queries (named ODXT) based on the Oblivious Cross-Tags...

Many recent studies focus on dynamic searchable encryption (DSE), which provides efficient data-search and data-update services directly on outsourced private data. Most encryption schemes are not optimized for update-intensive cases, which say that the same data record is frequently added and deleted from the database. How to build an efficient and secure DSE scheme for update-intensive data is still challenging. We propose UI-SE, the first DSE scheme that achieves single-round-trip...

Symmetric Searchable Encryption (SSE) allows users to outsource encrypted data to a possibly untrusted remote location while simultaneously being able to perform keyword search directly through the stored ciphertexts. An ideal SSE scheme should reveal no information about the content of the encrypted information nor about the searched keywords and their mapping to the stored files. However, most of the existing SSE schemes fail to fulfill this property since in every search query, some...

Volumetric leakage in encrypted databases had been overlooked by the community for a long time until Kellaris et al. (CCS ’16) proposed the first database reconstruction attack leveraging communication volume. Their attack was soon improved and several query recovery attacks were discovered recently. In response to the advancements of volumetric leakage attacks, volume-hiding searchable symmetric encryption (SSE) schemes have been proposed (Kamara and Moataz, Eurocrypt ’19 & Patel et al.,...

Most recently, Izza et al. propose a new ECC-based RFID authentication protocol by showing the vulnerabilities of Naeem's protocol. They claim that their scheme provides security and privacy. However, we assert that their protocol does not satisfy privacy including anonymity, untraceability, forward and backward secrecy on the contrary of their claim. We also argue that the scheme suffers from availability problems.

Dynamic searchable symmetric encryption (DSSE) has been widely recognized as a promising technique to delegate update and search queries over an outsourced database to an untrusted server while guaranteeing the privacy of data. Many efforts on DSSE have been devoted to obtaining a good tradeoff between security and performance. However, it appears that all existing DSSE works miss studying on what will happen if the DSSE client issues irrational update queries carelessly, such as duplicate...

Oblivious RAM (ORAM) enables a user to read/write her outsourced cloud data without access-pattern leakage. Not all users want a fully functional ORAM all the time since it always creates inefficiency. We show that forward-private/backward-private (FP/BP) ORAMs are also good alternatives for reducing the search-pattern leakage of dynamic searchable encryption (DSE). We introduce the FP/BP-ORAM definitions and present LL-ORAM, the first FP/BP-ORAM that achieves near-zero client storage,...

Recent research in Dynamic Searchable Symmetric Encryption (DSSE) focuses on efficient search over encrypted data while allowing updates. Unfortunately, as demonstrated by many attacks, updates can be a source of information leakage that can compromise DSSE privacy. To mitigate these attacks, forward and backward privacy of DSSE schemes have been introduced. A concerted effort of the research community has resulted in the publication of many DSSE schemes. To the best of our knowledge,...

Dynamic searchable symmetric encryption (SSE) supports updates and keyword searches in tandem on outsourced symmetrically encrypted data, while aiming to minimize the information revealed to the (untrusted) host server. The literature on dynamic SSE has identified two crucial security properties in this regard - forward and backward privacy. Forward privacy makes it hard for the server to correlate an update operation with previously executed search operations. Backward privacy limits the...

This paper initiates a new direction in the design and analysis of searchable symmetric encryption (SSE) schemes. We provide the first comprehensive security model and definition for SSE that takes into account leakage from the entirety of the SSE system, including not only from access to encrypted indices but also from access to the encrypted database documents themselves. Such system-wide leakage is intrinsic in end-to-end SSE systems, and can be used to break almost all state-of-the-art...

I describe a blockchain design that hides the transaction graph from Blockchain Analyzers. The design is based on the realization that today the miner creating a block needs enough information to verify the validity of transactions, which makes details about the transactions public and thus allows blockchain analysis. Some protocols, such as Mimblewimble, obscure the transaction amounts but not the source of the funds which is enough to allow for analysis. The insight in this technical note...

Incentive systems (such as customer loyalty systems) are omnipresent nowadays and deployed in several areas such as retail, travel, and financial services. Despite the benefits for customers and companies, this involves large amounts of sensitive data being transferred and analyzed. These concerns initiated research on privacy-preserving incentive systems, where users register with a provider and are then able to privately earn and spend incentive points. In this paper we construct an...

Due to its capabilities of searches and updates over the encrypted database, the dynamic searchable symmetric encryption (DSSE) has received considerable attention recently. To resist leakage abuse attacks, a secure DSSE scheme usually requires forward and backward privacy. However, the existing forward and backward private DSSE schemes either only support single keyword queries or require more interactions between the client and the server. In this paper, we first give a new leakage...

We study the problem of dynamic searchable encryption (DSE) with forward-and-backward privacy. Many DSE schemes have been proposed recently but the most efficient ones have one limitation: they require maintaining an operation counter for each unique keyword, either stored locally at the client or accessed obliviously (e.g., with an oblivious map) at the server, during every operation. We propose three new schemes that overcome the above limitation and achieve constant permanent client...

Secure messaging (SM) protocols allow users to communicate securely over untrusted infrastructure. In contrast to most other secure communication protocols (such as TLS, SSH, or Wireguard), SM sessions may be long-lived (e.g., years) and highly asynchronous. In order to deal with likely state compromises of users during the lifetime of a session, SM protocols do not only protect authenticity and privacy, but they also guarantee forward secrecy (FS) and post-compromise security (PCS). The...

Dynamic Searchable Symmetric Encryption (DSSE) enables a client to perform updates and searches on encrypted data which makes it very useful in practice. To protect DSSE from the leakage of updates (leading to break query or data privacy), two new security notions, forward and backward privacy, have been proposed recently. Although extensive attention has been paid to forward privacy, this is not the case for backward privacy. Backward privacy, first formally introduced by Bost et al., is...

Dynamic Searchable Symmetric Encryption ($\mathsf{DSSE}$), apart from providing support for search operation, allows a client to perform update operations on outsourced database efficiently. Two security properties, viz., forward privacy and backward privacy are desirable from a $\mathsf{DSSE}$ scheme. The former captures that the newly updated entries cannot be related to previous search queries and the latter ensures that search queries should not leak matching entries after they have been...

In this paper, we focus on the design of a novel authentication protocol that preserves the privacy of embedded devices. A Physically Unclonable Function (PUF) generates challenge-response pairs that form the source of authenticity between a server and multiple devices. We rely on Authenticated Encryption (AE) for confidentiality, integrity and authenticity of the messages. A challenge updating mechanism combined with an authenticate-before-identify strategy is used to provide privacy. The...

In the era of mass surveillance and information breaches, privacy of Internet communication, and messaging in particular, is a growing concern. As secure messaging protocols are executed on the not-so-secure end-user devices, and because their sessions are long-lived, they aim to guarantee strong security even if secret states and local randomness can be exposed. The most basic security properties, including forward secrecy, can be achieved using standard techniques such as authenticated...

Searchable encryption has received a significant attention from the research community with various constructions being proposed, each achieving asymptotically optimal complexity for specific metrics (e.g., search, update). Despite their elegancy, the recent attacks and deployment efforts have shown that the optimal asymptotic complexity might not always imply practical performance, especially if the application demands a high privacy. Hence, there is a significant need for searchable...

Using dynamic Searchable Symmetric Encryption, a user with limited storage resources can securely outsource a database to an untrusted server, in such a way that the database can still be searched and updated efficiently. For these schemes, it would be desirable that updates do not reveal any information a priori about the modifications they carry out, and that deleted results remain inaccessible to the server a posteriori. If the first property, called forward privacy, has been the main...

FIDO, German e-ID, Idemix and U-Prove constitute privacy-enhanced public-key infrastructures allowing users to authenticate in an anonymous way. This however hampers timely revocation in a privacy friendly way. From a legal perspective, revocation typically should be effective within 24 hours after user reporting. It should also be backward unlinkable, i.e. user anonymity cannot be removed after revocation. We describe a new, generic revocation mechanism based on pairing based encryption and...

Abstract: This work presents an Adaptively Secure Broadcast Mechanism (ASBM) based on threats analytics. It defines the security intelligence of a broadcast system comprehensively with a novel concept of collective intelligence. The algorithmic mechanism is analyzed from the perspectives of security intelligence, communication complexity and computational intelligence. The security intelligence of ASBM is defined in terms of authentication, authorization, correct identification, privacy:...

Privacy of RFID systems is receiving increasing attentions in the RFID community and an important issue required as to the security of RFID system. Backward privacy means the adversary can not trace the tag later even if he reveals the internal states of the tag sometimes before. In this paper, we analyze two recently proposed RFID authentication schemes: Randomized GPS and Randomized Hashed GPS scheme. We show both of them can not provide backward privacy in Juels and Weis privacy model,...

Radio Frequency IDentification based systems, which are the most famous example of ubiquitous networks, are getting pervasively deployed in many daily life applications where privacy sensitivity is entrusted to tag or server. In some applications, ownership transfer of RFID labels is another significant requirement. Specifically, the owner of RFID tags could be required to change several times during its lifetime. During the transfer, new owner first obtains necessary private information...