Description
In 1998, Blaze, Bleumer, and Strauss proposed a cryptographic primitive called proxy re-encryption, in which a proxy transforms - without seeing the corresponding plaintext - a ciphertext computed under Alice's public key into one that can be opened using Bob's secret key. Recently, an appropriate definition of chosen-ciphertext security and a construction fitting this model were put forth by Canetti and Hohenberger. Their system is bidirectional: the information released to divert ciphertexts from Alice to Bob can also be used to translate ciphertexts in the opposite direction. In this presentation, we will present the first construction of unidirectional proxy re-encryption scheme with chosen-ciphertext security in the standard model (i.e. without relying on the random oracle idealization), which solves a problem left open at CCS'07. Our construction is efficient and requires a reasonable complexity assumption in bilinear map groups. Like the Canetti-Hohenberger scheme, it ensures security according to a relaxed definition of chosen-ciphertext introduced by Canetti, Krawczyk and Nielsen. (joint work with Benoît Libert)
Next sessions
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Verification of Rust Cryptographic Implementations with Aeneas
Speaker : Aymeric Fromherz - Inria
From secure communications to online banking, cryptography is the cornerstone of most modern secure applications. Unfortunately, cryptographic design and implementation is notoriously error-prone, with a long history of design flaws, implementation bugs, and high-profile attacks. To address this issue, several projects proposed the use of formal verification techniques to statically ensure the[…] -
On the average hardness of SIVP for module lattices of fixed rank
Speaker : Radu Toma - Sorbonne Université
In joint work with Koen de Boer, Aurel Page, and Benjamin Wesolowski, we study the hardness of the approximate Shortest Independent Vectors Problem (SIVP) for random module lattices. We use here a natural notion of randomness as defined originally by Siegel through Haar measures. By proving a reduction, we show it is essentially as hard as the problem for arbitrary instances. While this was[…] -
Endomorphisms via Splittings
Speaker : Min-Yi Shen - No Affiliation
One of the fundamental hardness assumptions underlying isogeny-based cryptography is the problem of finding a non-trivial endomorphism of a given supersingular elliptic curve. In this talk, we show that the problem is related to the problem of finding a splitting of a principally polarised superspecial abelian surface. In particular, we provide formal security reductions and a proof-of-concept[…]-
Cryptography
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