References of "De Caro, Angelo"
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See detailReceiver and Sender Deniable Functional Encryption
De Caro, Angelo; Iovino, Vincenzo UL; O'Neill, Adam

in IET Information Security (2017)

Deniable encryption, first introduced by Canetti et al. (CRYPTO 1997), allows equivocation of encrypted communication. In this work we generalize its study to functional encryption (FE). Our results are ... [more ▼]

Deniable encryption, first introduced by Canetti et al. (CRYPTO 1997), allows equivocation of encrypted communication. In this work we generalize its study to functional encryption (FE). Our results are summarized as follows: We first put forward and motivate the concept of receiver deniable FE, for which we consider two models. In the first model, as previously considered by O'Neill et al. (CRYPTO 2011) in the case of identity-based encryption, a receiver gets assistance from the master authority to generate a fake secret key. In the second model, there are ``normal'' and ``deniable'' secret keys, and a receiver in possession of a deniable secret key can produce a fake but authentic-looking normal key on its own. In the first model, we show a compiler from any FE scheme for the general circuit functionality to a FE scheme having receiver deniability. In addition we show an efficient receiver deniable FE scheme for Boolean Formulae from bilinear maps. In the second (multi-distributional) model, we present a specific FE scheme for the general circuit functionality having receiver deniability. To our knowledge, a scheme in the multi-distributional model was not previously known even for the special case of identity-based encryption. Finally, we construct the first sender (non-multi-distributional) deniable FE scheme. [less ▲]

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See detailDeniable Functional Encryption
De caro, Angelo; Iovino, Vincenzo UL; O'Neill, Adam

in Public-key Cryptography - PKC 2016, 19th IACR International Conference on Practice and Theory in Public-Key Cryptography, Taipei, Taiwan, March 6-9, 2016, Proceedings, Part I (2016)

Deniable encryption, first introduced by Canetti et al. (CRYPTO 1997), allows a sender and/or receiver of encrypted communication to produce fake but authentic-looking coins and/or secret keys that “open” ... [more ▼]

Deniable encryption, first introduced by Canetti et al. (CRYPTO 1997), allows a sender and/or receiver of encrypted communication to produce fake but authentic-looking coins and/or secret keys that “open” the communication to a different message. Here we initiate its study for the more general case of functional encryption (FE), as introduced by Boneh et al. (TCC 2011), wherein a receiver in possession of a key k can compute from any encryption of a message x the value F (k, x) according to the scheme’s functionality F . Our results are summarized as follows: We put forth and motivate the concept of deniable FE, for which we consider two models. In the first model, as previously considered by O’Neill et al. (CRYPTO 2011) in the case of identity-based encryption, a receiver gets assistance from the master authority to generate a fake secret key. In the second model, there are “normal” and “deniable” secret keys, and a receiver in possession of a deniable secret key can produce a fake but authentic-looking normal key on its own. This parallels the “multi-distributional” model of deniability previously considered for public-key encryption. In the first model, we show that any FE scheme for the general circuit functionality (as several recent candidate construction achieve) can be converted into an FE scheme having receiver deniability, without introducing any additional assumptions. In addition we show an efficient receiver deniable FE for Boolean Formulae from bilinear maps. In the second (multi-distributional) model, we show a specific FE scheme for the general circuit functionality having receiver deniability. This result additionally assumes differing-inputs obfuscation and relies on a new technique we call delayed trapdoor circuits. To our knowledge, a scheme in the multi-distributional model was not previously known even in the simpler case of identity-based encryption. Finally, we show that receiver deniability for FE implies some form of simulation security, further motivating study of the latter and implying optimality of our results. [less ▲]

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See detailOn the Power of Rewinding Simulators in Functional Encryption
De Caro, Angelo; Iovino, Vincenzo UL

in Designs, Codes and Cryptography (2016)

In a seminal work, Boneh, Sahai and Waters (BSW, for short) [TCC'11] showed that for functional encryption the indistinguishability notion of security (IND-Security) is weaker than simulation-based ... [more ▼]

In a seminal work, Boneh, Sahai and Waters (BSW, for short) [TCC'11] showed that for functional encryption the indistinguishability notion of security (IND-Security) is weaker than simulation-based security (SIM-Security), and that SIM-Security is in general impossible to achieve. This has opened up the door to a plethora of papers showing feasibility and new impossibility results. Nevertheless, the quest for better definitions that (1) overcome the limitations of IND-Security and (2) the known impossibility results, is still open. In this work, we explore the benefits and the limits of using {\em efficient rewinding black-box simulators} to argue security. To do so, we introduce a new simulation-based security definition, that we call {\em rewinding simulation-based security} (RSIM-Security), that is weaker than the previous ones but it is still sufficiently strong to not meet pathological schemes as it is the case for IND-Security (that is implied by the RSIM). This is achieved by retaining a strong simulation-based flavour but adding more rewinding power to the simulator having care to guarantee that it can not learn more than what the adversary would learn in any run of the experiment. What we found is that for RSIM the BSW impossibility result does not hold and that IND-Security is {\em equivalent} to RSIM-Security for {\em Attribute-Based Encryption} in the {\em standard model}. Nevertheless, we prove that there is a setting where rewinding simulators are of no help. The adversary can put in place a strategy that forces the simulator to rewind continuously. [less ▲]

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See detailOn the Achievability of Simulation-Based Security for Functional Encryption
De caro, Angelo; Iovino, Vincenzo UL; Jain, Abhishek et al

in Advances in Cryptology - CRYPTO 2013 - 33rd Annual Cryptology Conference, Santa Barbara, CA, USA, August 18-22, 2013. Proceedings, Part II (2013)

This work attempts to clarify to what extent simulation-based security (SIM-security) is achievable for functional encryption (FE) and its relation to the weaker indistinguishability-based security (IND ... [more ▼]

This work attempts to clarify to what extent simulation-based security (SIM-security) is achievable for functional encryption (FE) and its relation to the weaker indistinguishability-based security (IND-security). Our main result is a compiler that transforms any FE scheme for the general circuit functionality (which we denote by Circuit-FE) meeting indistinguishability-based security (IND-security) to a Circuit-FE scheme meeting SIM-security, where: In the random oracle model, the resulting scheme is secure for an unbounded number of encryption and key queries, which is the strongest security level one can ask for. In the standard model, the resulting scheme is secure for a bounded number of encryption and non-adaptive key queries, but an unbounded number of adaptive key queries. This matches known impossibility results and improves upon Gorbunov et al. [CRYPTO’12] (which is only secure for non-adaptive key queries). Our compiler is inspired by the celebrated Fiat-Lapidot-Shamir paradigm [FOCS’90] for obtaining zero-knowledge proof systems from witness-indistinguishable proof systems. As it is currently unknown whether Circuit-FE meeting IND-security exists, the purpose of this result is to establish that it remains a good target for future research despite known deficiencies of IND-security [Boneh et al. – TCC’11, O’Neill – ePrint ’10]. We also give a tailored construction of SIM-secure hidden vector encryption (HVE) in composite-order bilinear groups. Finally, we revisit the known negative results for SIM-secure FE, extending them to natural weakenings of the security definition and thus providing essentially a full picture of the (in)achievability of SIM-secure FE. [less ▲]

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