Episode #125 of the Stack Overflow podcast is here. We talk Tilde Club and mechanical keyboards. Listen now
7

This concept is called targeted malleability: http://crypto.stanford.edu/~dabo/pubs/abstracts/reshom.html The abstract and introduction of that paper give a good overview of the ideas. In brief, the goal is to ensure that a homomorphic evaluator can only produce a ciphertext by evaluating a function from an "approved" class of functions. It is trivial to ...


5

it seems that you are looking for this paper of mine http://libeccio.dia.unisa.it/Papers/CHES/ Here we introduce the concept of a Controlled Homomorphic Encryption Scheme (CHES). In a CHES, for every circuit $C$, it is possible to homomorphically create a ciphertext of $C(m)$ from a ciphertext of $m$ (so far it is like a regular FHE) but only if a special ...


3

ABE provides a secure and automatic way to enforce access control, but access control may not involve encryption. In the ABE setting, the resources (that one wants to access) are encrypted by a "controller" and then the ciphertexts are made public and each user is granted a key corresponding to its specific access right. Then, the controller doesn't need ...


3

Not much, my impression is that the problems are more or less the same. People change the term to IoT because it sounds sexier than wireless sensors (and they can sell the same thing again as new). Another similar term is pervasive (ubiquitous) computing. Yet another related term is edge computing or fog computing. The main underlying research challenges ...


3

OT is typically not used as an application in its own right. In the context of access control, OT limits the number of messages received by B but not which messages. I don't know of any real applications for this (you could talk about a subscription where B has purchased the right to read any $k$ articles, but this is pretty artificial in my opinion). ...


2

By itself, no. Though research has been done to add the necessary features to make FHE circuit computation verifiable. These protocols would allow the one party to specify what can be computed on the encrypted data and then verify that the computation has been performed properly. Thus, it differs from Functional Encryption somewhat. In FE, the worker can ...


2

As stated in the comments we can't / won't advise on whether PolarSSL is suitable to perform the operations required. However, for your needs $N_1=N_2=N_3=32$ sounds like a reasonable choice, giving you a solid 256-bit security and no need to worry about truncation and the alike. As for $f_1$, HMAC-SHA256 sounds like the obvious choice, also giving you $...


2

I can discern two cases here: A strict hierarchy A partial hierarchy Using 1, "Hierarchical access control" as a term used with encryption implies that some users have more decryption power than others. Especially in access control modelling, hierarchy is usually "strict". This means that if A > B (A is "higher", and has "more" decryption power than B) ...


2

Attribute-Based Encryption (ABE) schemes are a way to securely send (i.e share) a plaintext (message) amongst some particular receivers. The data owner (sender) consider an access policy to encrypt the message under this policy that a data user (receiver) is able to decrypt the ciphertext if and only if he/she satisfies the policy. So the ABE schemes just ...


1

Access control is a broader concept that includes authentication, authorisation, accounting and possibly other components contributing to the control of access. Authorisation only concerns granting or denying permissions according to a security model and policies.


1

Potential Solution? Using Functional encryption, a trusted authority with a master secret key ($msk$) and public key ($pk$) would generate a "functional decryption" key ($sk$) from a participant's policy ($k$). Each participants would be provided the $pk$ and relative $sk$, where $sk$ is bound to the participant's public identity via a signed document. For ...


1

Probably not. When Bob at the end of the interaction finally computes the plaintext, it must be a function of everything he has obtained thus far; there's nothing stopping him from running the same computation again, unless you introduce some kind of special hardware or other additional assumptions. In other words, decryption is deterministic, and we know ...


1

Well, 1 way I could suggest is to encrypt the sensitive records with a more restrictive tree policy, obtain the cipher C and C', concatenate that ciphers with less sensitive records, encrypt that concatenation with a less restrictive tree policy and so on so forth.... Each level of encryption can be done with a new MK if u want a different secret s to be ...


1

Can the access policies defined using different access structures (Monotone Span Program and Access Trees) be used together in CP-ABE scheme? Yes. As Attribute-based signcryption with hybrid access policy (Yu and Cao, 2015) shows, it is possible to combine an Attribute-based Encryption scheme with an Attribute-based Signature scheme of different access ...


1

1) The meaning of a poset is that there may also be members $x,y \in X$, where neither $x \leqslant y$ nor $x \geqslant y$. Now consider such incomparable $x$ and $y$ with $parent(x)=parent(y)=w \in X$ and furthermore $u \in X, y=parent(u), x \nleqslant u, x \ngeqslant u$ Now $k(x)=f(k(w))=k(y)$. Then also $k(u)=f(f(k(w))=f(k(x))$, even though $x$ is not a ...


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