Multi-Identity And Mutative-Identity In Identity-Based Cryptography

In 1984,Shamir first proposed the notion of Identity-Based Cyptography(IBC), which includes the two notions of Identity-Based Encryption(IBE)and Identity-Based Signature(IBS).As a special public key cryptography,the property of IBC is that the public key is an arbitrary string,such that it can be a user's public information,where the corredponding private key is computed by a Trust Third Party.The merit of IBC system is that it can simply the managemeng of cerficiate due to that the public key actually is a cerficate and so it does not need a certificate to declare the relationship between the public key and the the user.We extend the notion of IBC and the aim is to achieve multi-single in private key management.Therefore,we extend two new notions from IBC,named Multi-Identity-Based Encryption(MIBE)and Mutative-Identity-Based Signature(MIBS). In MIBE,a single private key can map multiple public keys,such that we can use it to decrypt all ciphertexts encrypted in all these public keys.In MIBS,the single private key(singing key)maps a public key which can be mutative and the signer can decide which part of information should be released as the verification key.In this thesis,we show the following three results:1)The first MIBE scheme is based on Boneh-Franklin IBE.In our scheme,a single private key is euqal to n private keys of their scheme.That is,we can use our single private key to decrypt n kinds of ciphertexts encrypted in n different pulic keys and the length of the single privet key in our scheme is as short as that of one private key in Boneh-Franklin scheme.We prove its security in the random oracles model and this result was published in the proceeding of Pairing 2007.2)The second MIBE scheme is based on Boneh-Boyen IBE.In this scheme,we focus on how to prove its security without resorting to random oracles.We finally show that its security can be proved in selective-ID model and a single private key with two elements can map n different public keys.This result was published in the proceeding of Inscrypt 2007.3)The MIBS scheme is based on Paterson-Schuldt IBS.In this scheme,the public key is composed of compound identity,where there is a public information and n pieces of private information,and the private(signing)key only contains three elements.For each signature needing a different piece of private information,the signer can only leak the very private information for varification and hide all others to protect his/her private information.This result was published in the proceeding of CANS 2007.