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require various security assurances. This paper investigates one
particular assurance, query integrity, by which a database querier
(either the data owner or a third party) can verify that its queries
were faithfully executed by the cloud server with respect to the outsourced database. Query integrity is investigated in the setting of
dynamic databases, where the outsourced databases can be updated
by the data owners as needed. We present a formal security definition
of query integrity and a provably-secure efficient construction.
Our solution improves upon the state-of-the-art solutions by additionally allowing aggregate queries and more flexible join queries. In addition, we provide better performance by eliminating a linear factor in the extra storage complexity for security purpose. Our solution also achieves a trade-off between computational and communication complexities.
We exhibit formats that are guaranteed to avoid known filters, and give a framework for learning formats from non-censored HTTP traffic. These formats are put to use in our FTE record layer, to explore trade-offs between performance and steganographic capabilities. As one example, we visit the top 100 Alexa webpages through an FTE tunnel, incurring an average overhead of roughly 5%.
(mu-NIZK proof system); it provides a proof of \"the existence of a proof to a statement\". This meta-mathematical notion indeed seems redundant when we deal with proving NP statements, but in
the context of zero-knowledge theory and cryptography it has a large variety of applications.
Combined with another tool we develop which we call \"on-line simulatable NIZK proof system\", it is the key tool used to solve the open problem of the existence of a many prover non-interactive zero-knowledge system (MP-NIZK proof system). This problem was presented
by Micali when the important notion of non-interactive zero-knowledge proofs (NIZK) was rst suggested and implemented for a sole prover.
The solution immensely enlarges the domain of applications of the NIZK model. The work also provides a new connection between bounded (single-theorem) non-interactive zero-knowledge proofs and the unbounded (multi-theorem) one. This may help in reducing
the complexity assumption upon which to base NIZK systems.
Remark: This is a full version (with more details, more material, and with new proofs) of the Crypto 1990 paper on Metaproof. Over the years, the concept has been used and reinvented for specic settings beyond the original ones, by others; (which has made it more useful). Recently, we were asked about this paper and about details, so here they are! For historical reasons, except for this remark, this version is presented as it was in the above mentioned date under the above
aliations, though we did not pursue publication before!
in which user with secret key containing attributes, only able to decrypt the message if the attributes in the policy match with the attributes in secret key. The existing methods that use reasonably computable decryption policies produce the ciphertext of size at least linearly varying with the number of attributes with additional pairing operations during encryption and decryption. In this paper, we propose a scheme in which ciphertext remains constant in length, irrespective of the number of attributes. Our scheme works for a threshold case: the number of attributes in a policy must be a subset of attributes in a secret key. The security of propose scheme is based on Decisional Bilinear Diffie-Hellman (DBDH) problem.
between two parties who both know a weak secret w, such as a
password. (Such a setting is ubiquitous on the internet, where
passwords are the most commonly used security device.) We assume
that the key agreement protocol is taking place in the presence of
an active computationally unbounded adversary Eve. The adversary may
have partial knowledge about w, so we assume only that w has
some entropy from Eve\'s point of view. Thus, the goal of the
protocol is to convert this non-uniform secret w into a uniformly
distributed string $R$ that is fully secret from Eve. R may then
be used as a key for running symmetric cryptographic protocols (such
as encryption, authentication, etc.).
Because we make no computational assumptions, the entropy in R can
come only from w. Thus such a protocol must minimize the entropy
loss during its execution, so that R is as long as possible. The
best previous results have entropy loss of $\\Theta(\\kappa^2)$, where
$\\kappa$ is the security parameter, thus requiring the password to
be very long even for small values of $\\kappa$. In this work, we
present the first protocol for information-theoretic key agreement
that has entropy loss LINEAR in the security parameter. The
result is optimal up to constant factors. We achieve our improvement
through a somewhat surprising application of error-correcting codes
for the edit distance.
The protocol can be extended to provide also ``information
reconciliation,\'\' that is, to work even when the two parties have slightly different versions of w (for example, when biometrics are involved).
In this paper we propose a game-theoretic modelling of a particular form of security assessment -- one which addresses the question ``are we compromised?\'\'.
We do so by extending the recently proposed game ``FlipIt\'\', which itself can be used to model the interaction between defenders and attackers under the Advanced Persistent Threat (APT) scenario.
Our extension gives players the option to ``test\'\' the state of the game before making a move. This allows one to study the scenario in which organisations have the option to perform periodic security assessments of such nature, and the benefits they may bring.