Unifying Security Notions of Functional Encryption.

Functional encryption is an emerging paradigm for public-key encryption that enables finegrained control of access to encrypted data. In this work, we present new perspectives on security definitions for functional encryption, as well as new lower bounds on what can be achieved. Our main contributions are as follows: • We show a lower bound for functional encryption that satisfies a weak (non-adaptive) simulation-based security notion, via pseudo-random functions. This is the first lower bound that exploits unbounded collusions in an essential way. • We put forth and discuss a simulation-based notion of security for functional encryption, with an unbounded simulator (called USIM). We show that this notion interpolates indistinguishability and simulation-based security notions, and has strong correlations to results and barriers in the zero-knowledge and multi-party computation literature.Functional encryption is an emerging paradigm for public-key encryption that enables finegrained control of access to encrypted data. In this work, we present new perspectives on security definitions for functional encryption, as well as new lower bounds on what can be achieved. Our main contributions are as follows: • We show a lower bound for functional encryption that satisfies a weak (non-adaptive) simulation-based security notion, via pseudo-random functions. This is the first lower bound that exploits unbounded collusions in an essential way. • We put forth and discuss a simulation-based notion of security for functional encryption, with an unbounded simulator (called USIM). We show that this notion interpolates indistinguishability and simulation-based security notions, and has strong correlations to results and barriers in the zero-knowledge and multi-party computation literature.

Jan 1, 20128 citations

Simulation-Based Secure Functional Encryption in the Random Oracle Model.

Vincenzo Iovino, Karol Żebrowski

One of the main lines of research in functional encryption (FE) has consisted in studying the security notions for FE and their achievability. This study was initiated by [Boneh et al. { TCC’11, O’Neill { ePrint’10] where it was rst shown that for FE the indistinguishabilitybased (IND) security notion is not sucient in the sense that there are FE schemes that are provably IND-Secure but concretely insecure. For this reason, researchers investigated the achievability of Simulation-based (SIM) security, a stronger notion of security. Unfortunately, the above-mentioned works and others [e.g., Agrawal et al. { CRYPTO’13] have shown strong impossibility results for SIM-Security. One way to overcome these impossibility results was rstOne of the main lines of research in functional encryption (FE) has consisted in studying the security notions for FE and their achievability. This study was initiated by [Boneh et al. { TCC’11, O’Neill { ePrint’10] where it was rst shown that for FE the indistinguishabilitybased (IND) security notion is not sucient in the sense that there are FE schemes that are provably IND-Secure but concretely insecure. For this reason, researchers investigated the achievability of Simulation-based (SIM) security, a stronger notion of security. Unfortunately, the above-mentioned works and others [e.g., Agrawal et al. { CRYPTO’13] have shown strong impossibility results for SIM-Security. One way to overcome these impossibility results was rst

Jan 1, 20147 citations

Mergeable Functional Encryption

Vincenzo Iovino, Karol Żebrowski

Lecture notes in computer scienceJan 1, 20174 citations

Universal Composability Notion for Functional Encryption Schemes

Sadikin Rifki, Youngho Park, Kil-houm Park +1 more

We have developed an ideal functionality for security requirement of functional encryption schemes. The functionality is needed when we want to show the security of a functional encryption scheme in universal composable (UC) framework. A functionality $F_{fe}$ was developed to represent ideal respond of a functional encryption scheme against any polynomial time active attacker. We show that UC security notion of functional encryption scheme $F_{fe}$ is as strong as fully secure functional encryption in an indistinguishable game with chosen cipher text attack. The proof used a method that showing for any environment algorithm, it can not distinguish ideal world where the attacker play with ideal functionality $F_{fe}$ and real world where the attacker play a fully secure functional encryption scheme.We have developed an ideal functionality for security requirement of functional encryption schemes. The functionality is needed when we want to show the security of a functional encryption scheme in universal composable (UC) framework. A functionality $F_{fe}$ was developed to represent ideal respond of a functional encryption scheme against any polynomial time active attacker. We show that UC security notion of functional encryption scheme $F_{fe}$ is as strong as fully secure functional encryption in an indistinguishable game with chosen cipher text attack. The proof used a method that showing for any environment algorithm, it can not distinguish ideal world where the attacker play with ideal functionality $F_{fe}$ and real world where the attacker play a fully secure functional encryption scheme.

Journal of the Korea Industrial Information Systems ResearchJun 30, 20132 citations

Functional Encryption: Definitions and Challenges

Dan Boneh, Amit Sahai, Brent R. Waters

Lecture notes in computer scienceJan 1, 20111,048 citations

F_{fe}

was developed to represent ideal respond of a functional encryption scheme against any polynomial time active attacker. We show that UC security notion of functional encryption scheme

F_{fe}

is as strong as fully secure functional encryption in an indistinguishable game with chosen cipher text attack. The proof used a method that showing for any environment algorithm, it can not distinguish ideal world where the attacker play with ideal functionality

F_{fe}

and real world where the attacker play a fully secure functional encryption scheme.