4 results sorted by ID
Tighter Adaptive IBEs and VRFs: Revisiting Waters' Artificial Abort
Goichiro Hanaoka, Shuichi Katsumata, Kei Kimura, Kaoru Takemure, Shota Yamada
Public-key cryptography
One of the most popular techniques to prove adaptive security of identity-based encryptions (IBE) and verifiable random functions (VRF) is the partitioning technique. Currently, there are only two methods to relate the adversary's advantage and runtime $(\epsilon, {\sf T})$ to those of the reduction's ($\epsilon_{\sf proof}, {\sf T}_{\sf proof}$) using this technique: One originates to Waters (Eurocrypt 2005) who introduced the famous artificial abort step to prove his IBE, achieving...
Adaptively Secure Puncturable Pseudorandom Functions in the Standard Model
Susan Hohenberger, Venkata Koppula, Brent Waters
Foundations
We study the adaptive security of constrained PRFs in the standard model. We initiate our exploration with puncturable PRFs. A puncturable PRF family is a special class of constrained PRFs, where the constrained key is associated with an element $x'$ in the input domain. The key allows evaluation at all points $x\neq x'$.
We show how to build puncturable PRFs with adaptive security proofs in the standard model that involve only polynomial loss to the underlying assumptions. Prior work had...
Simulation without the Artificial Abort: Simplified Proof and Improved Concrete Security for Waters' IBE Scheme
Mihir Bellare, Thomas Ristenpart
Public-key cryptography
Waters' variant of the Boneh-Boyen IBE scheme is attractive because of its efficency, applications, and security attributes,but suffers from a relatively complex proof with poor concrete security. This is due in part to the proof's ``artificial abort'' step, which has then been inherited by numerous derivative works. It has often been asked whether this step is necessary. We show that it is not, providing a new proof
that eliminates this step. The new proof is not only simpler than the...
On (Hierarchical) Identity Based Encryption Protocols with Short Public Parameters \\ (With an Exposition of Waters' Artificial Abort Technique)
Sanjit Chatterjee, Palash Sarkar
Cryptographic protocols
At Eurocrypt 2005, Waters proposed an efficient identity based encryption (IBE) scheme. One drawback of this scheme is that the size of the public parameter is rather large. Our first contribution is a generalization of Waters scheme. In particular, we show that there is an interesting trade-off between the tightness of the security reduction and smallness of the public parameter size. For a given security level, this implies that if one reduces the public parameter size there is a...
One of the most popular techniques to prove adaptive security of identity-based encryptions (IBE) and verifiable random functions (VRF) is the partitioning technique. Currently, there are only two methods to relate the adversary's advantage and runtime $(\epsilon, {\sf T})$ to those of the reduction's ($\epsilon_{\sf proof}, {\sf T}_{\sf proof}$) using this technique: One originates to Waters (Eurocrypt 2005) who introduced the famous artificial abort step to prove his IBE, achieving...
We study the adaptive security of constrained PRFs in the standard model. We initiate our exploration with puncturable PRFs. A puncturable PRF family is a special class of constrained PRFs, where the constrained key is associated with an element $x'$ in the input domain. The key allows evaluation at all points $x\neq x'$. We show how to build puncturable PRFs with adaptive security proofs in the standard model that involve only polynomial loss to the underlying assumptions. Prior work had...
Waters' variant of the Boneh-Boyen IBE scheme is attractive because of its efficency, applications, and security attributes,but suffers from a relatively complex proof with poor concrete security. This is due in part to the proof's ``artificial abort'' step, which has then been inherited by numerous derivative works. It has often been asked whether this step is necessary. We show that it is not, providing a new proof that eliminates this step. The new proof is not only simpler than the...
At Eurocrypt 2005, Waters proposed an efficient identity based encryption (IBE) scheme. One drawback of this scheme is that the size of the public parameter is rather large. Our first contribution is a generalization of Waters scheme. In particular, we show that there is an interesting trade-off between the tightness of the security reduction and smallness of the public parameter size. For a given security level, this implies that if one reduces the public parameter size there is a...
