215 research outputs found
Leakage-Abuse Attacks Against Forward and Backward Private Searchable Symmetric Encryption
Dynamic searchable symmetric encryption (DSSE) enables a server to
efficiently search and update over encrypted files. To minimize the leakage
during updates, a security notion named forward and backward privacy is
expected for newly proposed DSSE schemes. Those schemes are generally
constructed in a way to break the linkability across search and update queries
to a given keyword. However, it remains underexplored whether forward and
backward private DSSE is resilient against practical leakage-abuse attacks
(LAAs), where an attacker attempts to recover query keywords from the leakage
passively collected during queries.
In this paper, we aim to be the first to answer this question firmly through
two non-trivial efforts. First, we revisit the spectrum of forward and backward
private DSSE schemes over the past few years, and unveil some inherent
constructional limitations in most schemes. Those limitations allow attackers
to exploit query equality and establish a guaranteed linkage among different
(refreshed) query tokens surjective to a candidate keyword. Second, we refine
volumetric leakage profiles of updates and queries by associating each with a
specific operation. By further exploiting update volume and query response
volume, we demonstrate that all forward and backward private DSSE schemes can
leak the same volumetric information (e.g., insertion volume, deletion volume)
as those without such security guarantees. To testify our findings, we realize
two generic LAAs, i.e., frequency matching attack and volumetric inference
attack, and we evaluate them over various experimental settings in the dynamic
context. Finally, we call for new efficient schemes to protect query equality
and volumetric information across search and update queries.Comment: A short version of this paper has been accepted to the 30th ACM
Conference on Computer and Communications Security (CCS'23
Balancing Security, Performance and Deployability in Encrypted Search
Encryption is an important tool for protecting data, especially data stored in the cloud. However, standard encryption techniques prevent efficient search. Searchable encryption attempts to solve this issue, protecting the data while still providing search functionality. Retaining the ability to search comes at a cost of security, performance and/or utility.
An important practical aspect of utility is compatibility with legacy systems. Unfortunately, the efficient searchable encryption constructions that are compatible with these systems have been proven vulnerable to attack, even against weaker adversary models.
The goal of this work is to address this security problem inherent with efficient, legacy compatible constructions. First, we present attacks on previous constructions that are compatible with legacy systems, demonstrating their vulnerability. Then we present two new searchable encryption constructions. The first, weakly randomized encryption, provides superior security to prior easily deployable constructions, while providing similar ease of deployment and query performance nearly identical to unencrypted databases. The second construction, EDDiES, provides much stronger security at the expense of a slight regression on performance.
These constructions show that it is possible to achieve a better balance of security and performance with the utility constraints that come with deployment in legacy systems
Certificate-Less Searchable Encryption with a Refreshing Keyword Search
Public Key Encryptions with Keyword Search (PEKS) scheme had been hosted for keeping data security and privacy of outsourced data in a cloud environment. It is also used to provide search operations on encrypted data. Nevertheless, most of the existing PEKS schemes are disposed to key-escrow problems due to the private key of the target users are known by the Key Generating Center (KGC). To improve the key escrow issue in PEKS schemes, the Certificate-Less Public Key Encryptions with Keyword Search (CL-PEKS) scheme has been designed. Meanwhile, the existing CL-PEKS schemes do not consider refreshing keyword searches. Due to this, the cloud server can store search trapdoors for keywords used in the system and can launch keyword guessing attacks. In this research work, we proposed Certificate-Less Searchable Encryption with a Refreshing Keyword Search (CL-SERKS) scheme by attaching date information to the encrypted data and keyword. We demonstrated that our proposed scheme is secure against adaptively chosen keyword attacks against both types of adversaries, where one adversary is given the power to select a random public key as a replacement for the user’s public key whereas another adversary is allowed to learn the system master key in the random oracle model under the Bilinear Diffie-Hellman problem assumption. We evaluated the performance of the proposed scheme in terms of both computational cost and communication cost. Experimental results show that the proposed CL-SERKS scheme has better computational cost during the key generation phase and testing phase than two related schemes. It also has lower communication costs than both related schemes
Power Range: Forward Private Multi-Client Symmetric Searchable Encryption with Range Queries Support
Symmetric Searchable Encryption (SSE) is an encryption technique that allows users to search directly over their outsourced encrypted data while preserving the privacy of both the files and the queries. In this paper, we present Power Range -- a dynamic SSE scheme (DSSE) that supports range queries in the multi-client model. We prove that our construction captures the very crucial notion of forward privacy in the sense that additions and deletions of files do not reveal any information about the content of past queries. Finally, to deal with the problem of synchronization in the multi-client model, we exploit the functionality offered by Trusted Execution Environments and Intel's SGX
Secure Remote Storage of Logs with Search Capabilities
Dissertação de Mestrado em Engenharia InformáticaAlong side with the use of cloud-based services, infrastructure and storage, the use of application logs
in business critical applications is a standard practice nowadays. Such application logs must be stored
in an accessible manner in order to used whenever needed. The debugging of these applications is a
common situation where such access is required. Frequently, part of the information contained in logs
records is sensitive.
This work proposes a new approach of storing critical logs in a cloud-based storage recurring to
searchable encryption, inverted indexing and hash chaining techniques to achieve, in a unified way, the
needed privacy, integrity and authenticity while maintaining server side searching capabilities by the logs
owner.
The designed search algorithm enables conjunctive keywords queries plus a fine-grained search
supported by field searching and nested queries, which are essential in the referred use case. To the
best of our knowledge, the proposed solution is also the first to introduce a query language that enables
complex conjunctive keywords and a fine-grained search backed by field searching and sub queries.A gerac¸ ˜ao de logs em aplicac¸ ˜oes e a sua posterior consulta s˜ao fulcrais para o funcionamento de qualquer
neg´ocio ou empresa. Estes logs podem ser usados para eventuais ac¸ ˜oes de auditoria, uma vez
que estabelecem uma baseline das operac¸ ˜oes realizadas. Servem igualmente o prop´ osito de identificar
erros, facilitar ac¸ ˜oes de debugging e diagnosticar bottlennecks de performance. Tipicamente, a maioria
da informac¸ ˜ao contida nesses logs ´e considerada sens´ıvel.
Quando estes logs s˜ao armazenados in-house, as considerac¸ ˜oes relacionadas com anonimizac¸ ˜ao,
confidencialidade e integridade s˜ao geralmente descartadas. Contudo, com o advento das plataformas
cloud e a transic¸ ˜ao quer das aplicac¸ ˜oes quer dos seus logs para estes ecossistemas, processos de
logging remotos, seguros e confidenciais surgem como um novo desafio. Adicionalmente, regulac¸ ˜ao
como a RGPD, imp˜oe que as instituic¸ ˜oes e empresas garantam o armazenamento seguro dos dados.
A forma mais comum de garantir a confidencialidade consiste na utilizac¸ ˜ao de t ´ecnicas criptogr ´aficas
para cifrar a totalidade dos dados anteriormente `a sua transfer ˆencia para o servidor remoto. Caso sejam
necess´ arias capacidades de pesquisa, a abordagem mais simples ´e a transfer ˆencia de todos os dados
cifrados para o lado do cliente, que proceder´a `a sua decifra e pesquisa sobre os dados decifrados.
Embora esta abordagem garanta a confidencialidade e privacidade dos dados, rapidamente se torna
impratic ´avel com o crescimento normal dos registos de log. Adicionalmente, esta abordagem n˜ao faz
uso do potencial total que a cloud tem para oferecer.
Com base nesta tem´ atica, esta tese prop˜oe o desenvolvimento de uma soluc¸ ˜ao de armazenamento
de logs operacionais de forma confidencial, integra e autˆ entica, fazendo uso das capacidades de armazenamento
e computac¸ ˜ao das plataformas cloud. Adicionalmente, a possibilidade de pesquisa sobre
os dados ´e mantida. Essa pesquisa ´e realizada server-side diretamente sobre os dados cifrados e sem
acesso em momento algum a dados n˜ao cifrados por parte do servidor..
Semantic Search Approach in Cloud
With the approach of cloud computing, more and more information data are distributed to the public cloud for economic savings and ease of access. But, the encryption of privacy information is necessary to guarantee the security. Now a days efficient data utilization, and search over encrypted cloud data has been a great challenge. Solution of existing methods depends only on the keyword of submitted query and didn�t examine the semantics of keyword. Thus the search schemes are not intelligent and also omit some semantically related documents. To overcome this problem, we propose a semantic expansion based similar search solution over encrypted cloud data. The solution of this method will return not only the exactly matched files, but also the files including the terms semantically related to the query keyword. In this scheme, a corresponding file metadata is constructed for each file. After this, both the encrypted file metadata set and file collection are uploaded to the cloud server. With the help of metadata set file, the cloud server maintains the inverted index and create semantic relationship library (SRL) for the keywords set. After receiving a query request from user , this server firstly search out the keywords that are related to the query keyword according to SRL. After this, both the query keyword and the extensional words are used to retrieve the files to fulfill the user request. These files are returned in order according to the total relevance score. Our detailed security analysis shows that our method is privacy-preserving and secure than the previous searchable symmetric encryption (SSE) security definition. Experimental evaluation demonstrates the efficiency and effectives of the scheme
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