Identity-based cryptosystems and signature schemes
Proceedings of CRYPTO 84 on Advances in cryptology
Random oracles are practical: a paradigm for designing efficient protocols
CCS '93 Proceedings of the 1st ACM conference on Computer and communications security
Identity-Based Encryption from the Weil Pairing
CRYPTO '01 Proceedings of the 21st Annual International Cryptology Conference on Advances in Cryptology
Secure Integration of Asymmetric and Symmetric Encryption Schemes
CRYPTO '99 Proceedings of the 19th Annual International Cryptology Conference on Advances in Cryptology
Key-Privacy in Public-Key Encryption
ASIACRYPT '01 Proceedings of the 7th International Conference on the Theory and Application of Cryptology and Information Security: Advances in Cryptology
An Identity Based Encryption Scheme Based on Quadratic Residues
Proceedings of the 8th IMA International Conference on Cryptography and Coding
How to Enhance the Security of Public-Key Encryption at Minimum Cost
PKC '99 Proceedings of the Second International Workshop on Practice and Theory in Public Key Cryptography
Proceedings of the 2003 ACM workshop on Privacy in the electronic society
Concealing complex policies with hidden credentials
Proceedings of the 11th ACM conference on Computer and communications security
Multi-authority attribute based encryption
TCC'07 Proceedings of the 4th conference on Theory of cryptography
Applying fujisaki-okamoto to identity-based encryption
AAECC'06 Proceedings of the 16th international conference on Applied Algebra, Algebraic Algorithms and Error-Correcting Codes
Searchable encryption revisited: consistency properties, relation to anonymous IBE, and extensions
CRYPTO'05 Proceedings of the 25th annual international conference on Advances in Cryptology
Anonymous hierarchical identity-based encryption (without random oracles)
CRYPTO'06 Proceedings of the 26th annual international conference on Advances in Cryptology
Practical identity-based encryption without random oracles
EUROCRYPT'06 Proceedings of the 24th annual international conference on The Theory and Applications of Cryptographic Techniques
ACISP'06 Proceedings of the 11th Australasian conference on Information Security and Privacy
Efficient identity-based key encapsulation to multiple parties
IMA'05 Proceedings of the 10th international conference on Cryptography and Coding
Building Key-Private Public-Key Encryption Schemes
ACISP '09 Proceedings of the 14th Australasian Conference on Information Security and Privacy
Broadcast encryption with multiple trust authorities
LATINCRYPT'10 Proceedings of the First international conference on Progress in cryptology: cryptology and information security in Latin America
Identity based encryption: Progress and challenges
Information Security Tech. Report
Anonymous broadcast encryption: adaptive security and efficient constructions in the standard model
PKC'12 Proceedings of the 15th international conference on Practice and Theory in Public Key Cryptography
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We consider the security of Identity-Based Encryption (IBE) in the setting of multiple Trusted Authorities (TAs). In this multi-TA setting, we envisage multiple TAs sharing some common parameters, but each TA generating its own master secrets and master public keys. We provide security notions and security models for the multi-TA setting which can be seen as natural extensions of existing notions and models for the single-TA setting. In addition, we study the concept of TA anonymity, which formally models the inability of an adversary to distinguish two ciphertexts corresponding to the same message and identity but generated using different TA master public keys. We argue that this anonymity property is a natural one of importance in enhancing privacy and limiting traffic analysis in multi-TA environments. We study a modified version of a Fujisaki-Okamoto conversion in the multi-TA setting, proving that our modification lifts security and anonymity properties from the CPA to the CCA setting. Finally, we apply these results to study the security of the Boneh-Franklin and Sakai-Kasahara IBE schemes in the multi-TA setting.