References of "Rosie, Razvan 50033778"
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See detailRobust Encryption, Extended
Geraud, Remi; Naccache, David; Rosie, Razvan UL

in Matsui, Mitsuru (Ed.) The Cryptographers' Track at the RSA Conference 2019, San Francisco, CA, USA, March 4–8, 2019, Proceedings (2019, March 01)

Robustness is a notion often tacitly assumed while working with encrypted data. Roughly speaking, it states that a ciphertext cannot be decrypted under different keys. Initially formalized in a public-key ... [more ▼]

Robustness is a notion often tacitly assumed while working with encrypted data. Roughly speaking, it states that a ciphertext cannot be decrypted under different keys. Initially formalized in a public-key context, it has been further extended to key-encapsulation mechanisms, and more recently to pseudorandom functions, message authentication codes and authenticated encryption. In this work, we motivate the importance of establishing similar guarantees for functional encryption schemes, even under adversarially generated keys. Our main security notion is intended to capture the scenario where a ciphertext obtained under a master key (corresponding to Authority 1) is decrypted by functional keys issued under a different master key (Authority 2). Furthermore, we show there exist simple functional encryption schemes where robustness under adversarial key-generation is not achieved. As a secondary and independent result, we formalize robustness for digital signatures – a signature should not verify under multiple keys – and point out that certain signature schemes are not robust when the keys are adversarially generated. We present simple, generic transforms that turn a scheme into a robust one, while maintaining the original scheme’s security. For the case of public-key functional encryption, we look into ciphertext anonymity and provide a transform achieving it. [less ▲]

Detailed reference viewed: 59 (5 UL)
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See detailNew Constructions of Verifiable Delay Functions
Barthel, Jim Jean-Pierre UL; Naccache, David; Rosie, Razvan UL

E-print/Working paper (n.d.)

A Verifiable Delay Function (VDF) is a cryptographic protocol thought to provide a proof of elapsed time. At the core of such a protocol lies a sequential task whose evaluation cannot be accelerated, even ... [more ▼]

A Verifiable Delay Function (VDF) is a cryptographic protocol thought to provide a proof of elapsed time. At the core of such a protocol lies a sequential task whose evaluation cannot be accelerated, even in the presence of massive parallel computational resources. We introduce a novel sequentiality assumption, put forth a scheme that achieves this sequentiality constraint by requiring its users to evaluate a function over (levelled) fully homomorphic ciphertexts and provide a heuristic security analysis. [less ▲]

Detailed reference viewed: 77 (5 UL)