## CryptoDB

### Philippe Gaborit

#### Publications

Year
Venue
Title
2019
EUROCRYPT
We describe a variation of the Schnorr-Lyubashevsky approach to devising signature schemes that is adapted to rank based cryptography. This new approach enables us to obtain a randomization of the signature, which previously seemed difficult to derive for code-based cryptography. We provide a detailed analysis of attacks and an EUF-CMA proof for our scheme. Our scheme relies on the security of the Ideal Rank Support Learning and the Ideal Rank Syndrome problems and a newly introduced problem: Product Spaces Subspaces Indistinguishability, for which we give a detailed analysis. Overall the parameters we propose are efficient and comparable in terms of signature size to the Dilithium lattice-based scheme, with a signature size of 4 kB for a public key of size less than 20 kB.
2017
CRYPTO
2014
EPRINT
2014
EPRINT
2010
CRYPTO
2008
EPRINT
Homomorphic encryption schemes are an essential ingredient to design protocols where different users interact in order to obtain some information from the others, at the same time that each user keeps private some of his information. When the algebraic structure underlying these protocols is complicated, then standard homomorphic encryption schemes are not enough, because they do not allow to crypto-compute at the same time additions and products of plaintexts. In this work we define a theoretical object, $t$-chained encryption schemes, which can be used to design crypto-computers for the addition and product of $t$ integer values. Previous solutions in the literature worked for the case $t=2$. Our solution is not only theoretical: we show that some existing (pseudo-)homomorphic encryption schemes (some of them based on lattices) can be used to implement in practice the concept of $t$-chained encryption scheme.
2007
EPRINT
A PIR scheme is a scheme that allows an user to get an element of a database without giving any information about what part of the database he is interested in. In this paper we present a lattice-based PIR scheme, using an NTRU-like approach, in which the computational cost is a few thousand bit-operations per bit in the database. This improves the protocol computational performance by two orders of magnitude when compared to existing approaches. Our scheme has worse communication performance than other existing protocols, but we show that practical usability of PIR schemes is not as dependent on communication performance as the literature suggests, and that a trade-off between communication and computation leads to much more versatile schemes.
2006
EUROCRYPT