International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Yannick Seurin

Affiliation: ANSSI, France

Publications

Year
Venue
Title
2019
EUROCRYPT
Aggregate Cash Systems: A Cryptographic Investigation of Mimblewimble 📺
Mimblewimble is an electronic cash system proposed by an anonymous author in 2016. It combines several privacy-enhancing techniques initially envisioned for Bitcoin, such as Confidential Transactions (Maxwell, 2015), non-interactive merging of transactions (Saxena, Misra, Dhar, 2014), and cut-through of transaction inputs and outputs (Maxwell, 2013). As a remarkable consequence, coins can be deleted once they have been spent while maintaining public verifiability of the ledger, which is not possible in Bitcoin. This results in tremendous space savings for the ledger and efficiency gains for new users, who must verify their view of the system.In this paper, we provide a provable-security analysis for Mimblewimble. We give a precise syntax and formal security definitions for an abstraction of Mimblewimble that we call an aggregate cash system. We then formally prove the security of Mimblewimble in this definitional framework. Our results imply in particular that two natural instantiations (with Pedersen commitments and Schnorr or BLS signatures) are provably secure against inflation and coin theft under standard assumptions.
2017
CRYPTO
2017
CRYPTO
2017
TOSC
Reconsidering the Security Bound of AES-GCM-SIV
Tetsu Iwata Yannick Seurin
We make a number of remarks about the AES-GCM-SIV nonce-misuse resistant authenticated encryption scheme currently considered for standardization by the Crypto Forum Research Group (CFRG). First, we point out that the security analysis proposed in the ePrint report 2017/168 is incorrect, leading to overly optimistic security claims. We correct the bound and re-assess the security guarantees offered by the scheme for various parameters. Second, we suggest a simple modification to the key derivation function which would improve the security of the scheme with virtually no efficiency penalty.
2017
TOSC
New Constructions of MACs from (Tweakable) Block Ciphers
We propose new constructions of Message Authentication Codes (MACs) from tweakable or conventional block ciphers. Our new schemes are either stateless and deterministic, nonce-based, or randomized, and provably secure either in the standard model for tweakable block cipher-based ones, or in the ideal cipher model for block cipher-based ones. All our constructions are very efficient, requiring only one call to the underlying (tweakable) block cipher in addition to universally hashing the message. Moreover, the security bounds we obtain are quite strong: they are beyond the birthday bound, and nonce-based/randomized variants provide graceful security degradation in case of misuse, i.e., the security bound degrades linearly with the maximal number of repetitions of nonces/random values.
2016
CRYPTO
2016
CRYPTO
2016
FSE
2016
JOFC
2015
EPRINT
2015
EPRINT
2015
EPRINT
2015
EPRINT
2015
EPRINT
2015
EPRINT
2015
EPRINT
2015
EPRINT
2015
FSE
2015
EUROCRYPT
2015
CRYPTO
2015
CRYPTO
2015
ASIACRYPT
2014
CRYPTO
2014
PKC
2014
EPRINT
2014
EPRINT
2014
FSE
2013
PKC
2013
ASIACRYPT
2013
FSE
2012
TCC
2012
EUROCRYPT
2012
ASIACRYPT
2010
TCC
2008
EUROCRYPT
2008
EPRINT
HB#: Increasing the Security and Efficiency of HB+
The innovative HB+ protocol of Juels and Weis [10] extends device authentication to low-cost RFID tags. However, despite the very simple on-tag computation there remain some practical problems with HB+ and despite an elegant proof of security against some limited active attacks, there is a simple man-in-the-middle attack due to Gilbert et al. [8]. In this paper we consider improvements to HB+ in terms of both security and practicality. We introduce a new protocol that we denote random-HB#. This proposal avoids many practical drawbacks of HB+, remains provably resistant to attacks in the model of Juels and Weis, and at the same time is provably resistant to a broader class of active attacks that includes the attack of [8]. We then describe an enhanced variant called HB# which offers practical advantages over HB+.
2008
EPRINT
The Random Oracle Model and the Ideal Cipher Model are Equivalent
The Random Oracle Model and the Ideal Cipher Model are two well known idealised models of computation for proving the security of cryptosystems. At Crypto 2005, Coron et al. showed that security in the random oracle model implies security in the ideal cipher model; namely they showed that a random oracle can be replaced by a block cipher-based construction, and the resulting scheme remains secure in the ideal cipher model. The other direction was left as an open problem, i.e. constructing an ideal cipher from a random oracle. In this paper we solve this open problem and show that the Feistel construction with 6 rounds is enough to obtain an ideal cipher; we also show that 5 rounds are insufficient by providing a simple attack. This contrasts with the classical Luby-Rackoff result that 4 rounds are necessary and sufficient to obtain a (strong) pseudo-random permutation from a pseudo-random function.
2008
CHES
2008
EUROCRYPT
2008
CRYPTO
2007
CHES
2007
FSE

Program Committees

FSE 2019
FSE 2018
Crypto 2017
FSE 2017
Crypto 2016
Eurocrypt 2016
FSE 2016
Eurocrypt 2013