Multi-identity management for identity-based cryptography

Abstract

In identity-based (or ID-based) cryptography, user identities can be employed as public keys, where each public key maps a unique private key generated by a trusted authority usually called Private Key Generator (PKG). In some situations, a user could hold multiple identities; therefore, he has to manage the same number of private keys. This adds extra work to the user, especially when the number is large. In this paper, we tackle this issue by proposing two novel key management schemes that allow a single private key to map multiple public keys (identities). We name them Multi-Identity-Based Encryption (MIBE) and Mutable Identity-Based Signature (MIBS), respectively. In MIBE scheme, a single private key can be used to decrypt multiple ciphertexts encrypted with different public keys associated to the single private key. In MIBS, there is only a single private key that maps various public keys (identities).We refer to this property of public keys as mutable. We also provide complete security analysis to our schemes.