Bernardo Machado David

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This paper presents efficient structure-preserving signature schemes based on simple assumptions such as decisional linear. We first give two general frameworks for constructing fully secure signature schemes from weaker building blocks such as variations of one-time signatures and random message secure signatures. They can be seen as refinements of the(More)
We present an efficient structure-preserving tagged one-time signature scheme with tight security reductions to the decision-linear assumption. Our scheme features short tags consisting of a single group element and gives rise to the currently most efficient structure-preserving signature scheme based on the decision-liner assumption with constant-size(More)
Single sign-on solutions allow users to sign on only once and have their identities automatically verified by each application or service they want to access afterwards. There are few practical and secure single sign-on models, even though it is of great importance to current distributed application environments. We build on proxy signature schemes to(More)
We present a new compact verifiable secret sharing scheme, based on this we present the first construction of a homomorphic UC commitment scheme that requires only cheap symmetric cryptography, except for a small number of seed OTs. To commit to a k-bit string, the amortized communication cost is O(k) bits. Assuming a sufficiently efficient pseudorandom(More)
We propose the first UC secure commitment scheme with (amortized) computational complexity linear in the size of the string committed to. After a preprocessing phase based on oblivious transfer, that only needs to be done once and for all, our scheme only requires a pseudorandom generator and a linear code with efficient encoding. We also construct an(More)
We propose the first UC commitment scheme for binary strings with the optimal properties of rate approaching 1 and linear time (in the amortised sense, using a small number of seed OTs). On top of this, the scheme is additively homomorphic, which allows for applications to maliciously secure 2-party computation. As tools for obtaining this, we make three(More)