1,720,999 research outputs found
Type-preserving matrices and security of block ciphers
Full text linkWe introduce a new property for mixing layers which guarantees protection against algebraic attacks based on the imprimitivity of the group generated by the round functions. Mixing layers satisfying this property are called non-type-preserving. Our main result is to characterize such mixing layers by providing a list of necessary and sufficient conditions on the structure of their underlying binary matrices. Then we show how several families of linear maps are non-type-preserving, including the mixing layers of AES, GOST and PRESENT. Finally we prove that the group generated by the round functions of an SPN cipher with addition modulo 2 n as key mixing function is primitive if its mixing layer satisfies this property
Inner product functional encryption based on the UOV scheme
No full textWe analyze the efficiency and security of the Inner Product Functional Encryption (IPFE) protocol
introduced in 2021 by Debnath, Mesnager, Dey, and Kundu, specifically when instantiated with UOV.
While the scheme offers several advantages, including improvements in key generation and encryption/decryption
algorithms, along with compact key sizes, the decryption algorithm remains exponential in complexity
with respect to the security parameter. To address this limitation, we propose a variant aimed
at reducing the decryption cost. However, this alternative remains impractical at present due to
the resulting large ciphertext size
History-Free Sequential Aggregation of Hash-and-Sign Signatures
Full text linkA sequential aggregate signature (SAS) scheme allows multiple users to sequentially combine their respective signatures in order to reduce communication costs. Historically, early proposals required the use of trapdoor permutation (e.g., RSA). In recent years, a number of attempts have been made to extend SAS schemes to post-quantum assumptions. Many post-quantum signatures have been proposed in the hash-and-sign paradigm, which requires the use of trapdoor functions and appears to be an ideal candidate for sequential aggregation attempts. However, the hardness in achieving post-quantum one-way permutations makes it difficult to obtain similarly general constructions. Direct attempts at generalizing permutation-based schemes have been proposed, but they either lack formal security or require additional properties on the trapdoor function, which are typically not available for multivariate or code-based functions. In this paper, we propose a (partial-signature) history-free SAS within the probabilistic hash-and-sign with retry paradigm, generalizing existing techniques to generic trapdoor functions. We prove the security of our scheme in the random oracle model and we instantiate our construction with three post-quantum schemes, comparing their compression capabilities. Finally, we discuss how direct extensions of permutation-based SAS schemes are not possible without additional properties, showing the lack of security of two existing multivariate schemes
Group factorisation for smaller signatures from cryptographic group actions
Full text linkCryptographic group actions have gained significant attention in recent years for their application on post-quantum Sigma protocols and digital signatures. In NIST’s recent additional
call for post-quantum signatures, three relevant proposals are based on group actions: LESS,
MEDS, and ALTEQ. This work explores signature optimisations leveraging a group’s factorisation. We show that if the group admits a factorisation as a semidirect product of subgroups,
the group action can be restricted on a quotient space under the equivalence relation induced
by the factorisation. If the relation is efficiently decidable, we show that it is possible to
construct an equivalent Sigma protocol for a relationship that depends only on one of the
subgroups. Moreover, if a special class of representative of the quotient space is efficiently
computable via a canonical form, the restricted action is effective and does not incur in
security loss. Finally, we apply these techniques to the group actions underlying LESS and
MEDS, showing how they will affect the length of signatures and public keys
Designs, Efficiency and Decentralised Applications of Threshold Schnorr Signatures
Full text linkThis survey presents some threshold variants of the Schnorr signature scheme selected according to their novelty or theoretical relevance, and evaluates them on four metrics: security guarantees, computational complexity, memory complexity and bandwidth requirements.
We will then exploit them to provide a few comparisons in the case of real-world applications, such as blockchain and custodianship
Security issues of CFS-like digital signature algorithms
Full text linkWe analyze the security of some variants of the CFS code-based digital signature
scheme. We show how the adoption of some code-based hash functions to improve the
efficiency of CFS leads to the ability of an attacker to produce a forgery compatible with the
rightful user’s public key
A Survey on PoW-based Consensus
Full text linkWe provide a historical overview of proof-of-work techniques and the fields in which it plunges its roots. We are interested in PoW-techniques applied to blockchain technology and therefore we survey the state-of-the-art protocols employing these methods for consensus algorithms, emphasizing the differences between the efficient hashcash systems and the promising bread pudding protocols. Afterwards, the consensus mechanisms are discussed and some interesting known attacks to these algorithms are collected and classified according to their underlying ideas
Sobre la visión de Dante y el arte italiano de su tiempo
No full textRessenya del llibre: Maria Luisa Meneghetti, Alessio Monciatti, Stefano Resconi (ed.), Con gli ochi di Dante. L’Italia artística nell’Età della Commedia, catàleg de l’exposició, Roma, Bardi edizioni, 2022.Book review: Maria Luisa Meneghetti, Alessio Monciatti, Stefano Resconi (ed.), Con gli ochi di Dante. L’Italia artística nell’Età della Commedia, catàleg de l’exposició, Roma, Bardi edizioni, 2022.Reseña del libro: Maria Luisa Meneghetti, Alessio Monciatti, Stefano Resconi (ed.), Con gli ochi di Dante. L’Italia artística nell’Età della Commedia, catàleg de l’exposició, Roma, Bardi edizioni, 2022
Extensible decentralized secret sharing and application to Schnorr signatures
No full textStarting from links between Coding Theory and Secret Sharing Schemes, we develop an extensible and decentralized version of Shamir Secret Sharing, that allows the addition of new users after the initial share distribution. On top of it we design a totally decentralized (t, n)-threshold Schnorr signature scheme that needs only t users online during the key generation phase, while the others join later. Under standard assumptions we prove our scheme secure against adaptive malicious adversaries. Furthermore, we show how our security notion can be strengthened when considering a rushing adversary. Using a classical game-based argument, we prove that if there is an adversary capable of forging the scheme with non-negligible probability, then we can build a forger for the centralized Schnorr scheme with non-negligible probability
Con gli occhi di Dante. L’Italia artistica nell’età della Commedia, catalogo della mostra, Roma, Palazzina dell’Auditorio - Villa Farnesina (26 marzo - 25 giugno 2022), a cura di Maria Luisa Meneghetti, Alessio Monciatti, Stefano Resconi, con la collaborazione di Mario Cobuzzi, Roma, Bardi, 2022, pp. xxiii + 440
No full textRecensione di Con gli occhi di Dante. L’Italia artistica nell’età della Commedia, catalogo
della mostra, Roma, Palazzina dell’Auditorio - Villa Farnesina (26 marzo - 25 giugno 2022), a cura di Maria Luisa Meneghetti, Alessio Monciatti, Stefano Resconi, con la collaborazione di Mario
Cobuzzi, Roma, Bardi, 2022, pp. xxiii + 440
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