• Journal of Korea Society of Industrial Information Systems
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• v.18 no.3
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• pp.17-26
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• 2013

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 Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.57-70
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• 2014

Inner product encryption (IPE) scheme is a cryptographic primitive that provides fine grained relations between secret keys and ciphertexts. This paper proposes a new IPE scheme which achieves fully attribute hiding security. Our IPE scheme is based on bilinear groups of a composite order. We prove the fully attribute hiding security of our IPE by using dual encryption system framework. In performance analysis, we compare the computation cost and memory requirement of our proposed IPE to other existing IPE schemes.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.1
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• pp.20-34
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• 2009

We newly propose a multiple and unlinkable identity-based public key encryption scheme which allows the use of a various number of identity-based public keys in different groups or applications while keeping a single decryption key so that the decryption key can decrypt every ciphertexts encrypted with those public keys. Also our scheme removes the use of certificates as well as the key escrow problem so it is functional and practical. Since our public keys are unlinkable, the user's privacy can be protected from attackers who collect and trace the user information and behavior using the known public keys. Furthermore, we suggest a decryption key renewal protocol to strengthen the security of the single decryption key. Finally, we prove the security of our scheme against the adaptive chosen-ciphertext attack under the random oracle model.