• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.6B
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• pp.199-206
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• 2008

Broadcast encryption is a cryptographical primitive which is designed for a content provider to distribute contents to only privileged qualifying users through an insecure channel. Anyone who knows public keys can distribute contents by means of public key broadcast encryption whose technique can also be applicable to many other applications. In order to design public key broadcast encryption scheme, it should devise some methods that convert a broadcast encryption scheme based on symmetric key cryptosystem to a public key broadcast encryption. Up to this point, broadcast encryption scheme on trial for converting from symmetric key setting to asymmetric public key setting has been attempted by employing the Hierarchical Identity Based Encryption (HIBE) technique. However, this converting method is not optimal because some of the properties of HIBE are not quite fitting for public key broadcast schemes. In this paper, we proposed new converting method and an efficient public key broadcast encryption scheme Pub-PI which is obtained by adapting the new converting method to the PI scheme [10]. The transmission overhead of the Pub-PI is approximately 3r, where r is the number of revoked users. The storage size of Pub-PI is O($c^2$), where c is a system parameter of PI and the computation cost is 2 pairing computations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4680-4700
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• 2015

Broadcast encryption is an efficient way to distribute confidential information to a set of receivers using broadcast channel. It allows the broadcaster to dynamically choose the receiver set during each encryption. However, most broadcast encryption schemes in the literature haven't taken into consideration the receiver's privacy protection, and the scanty privacy preserving solutions are often less efficient, which are not suitable for practical scenarios. In this paper, we propose an efficient dynamic anonymous broadcast encryption scheme that has the shortest ciphertext length. The scheme is constructed over the composite order bilinear groups, and adopts the Lagrange interpolation polynomial to hide the receivers' identities, which yields efficient decryption algorithm. Security proofs show that, the proposed scheme is both secure and anonymous under the threat of adaptive adversaries in standard model.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.07a
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• pp.11-16
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• 2003

본 논문에서는 새로운 공개키 다중채널 broadcast encryption scheme(이하 PK-MCBE라 부른다)을 제안한다. 일반적인 broadcast encryption은 하나의 채널스트림을 전송하는 반면 PK-MCBE는 다수채널의 컨텐츠 스트림을 전송한다. 본 논문에서 제안하는 방식에서 수신자는 단지 하나의 비밀키만을 필요로 하며 한번 받은 비밀키는 변경되지 않는다. 제안하는 방식에서는 각 채널당 송신자가 전송하는 메세지의 공통부분을 한번만 전송하여 전체 전송 메세지의 길이를 줄일 수 있다. 또한 배신자(traitors)를 추적하여 효과적으로 강제 탈퇴시킬 수 있다.

• Journal of Broadcast Engineering
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• v.19 no.4
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• pp.502-509
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• 2014

Broadcast encryption is a cryptographic primitive that allows a sender to securely transmit a message to a set of receivers. The most influential broadcast encryption system was proposed in 2001 by Naor, Naor, Lotspiech, based on binary trees and the Subset Difference (SD) method. In 2006, Jang, Nyang, and Song suggested a new broadcast encryption system that can reduce transmission rate by 50% compared to the SD method, by introducing the so-called '2-SD' method. Their result was later given the registration of a patent in Korea (registration number: 100879083). Unfortunately, however, this paper shows that Jang et. al.'s broadcast encryption system is not secure against collusion attacks that are considered as being the basic security requirement in designing broadcast encryption.

• Journal of Broadcast Engineering
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• v.20 no.4
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• pp.580-597
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• 2015

Broadcast encryption system is a cryptographic primitive that enables a sender to broadcast a message to a set of receivers in a secure channel. Out of previous proposed broadcast encryption systems, the most effective is the one that uses the Subset Difference(SD) method in a binary tree structure. The SD method has been realized by two underlying approaches: Pseudo-Random Generator(PRG) and Secret Sharing(SS). 2-SD method is the generalized version of the SD method by which two subsets of revoked receivers can be dealt with by one subset (in an SD-based broadcast encryption system). The primary advantage of the 2-SD method is to further reduce the size of transmission overhead, compared to the SD method. Until now, however, there is no known broadcast encryption system that is based on such a 2-SD technique using either PRG or SS basis. In this paper, we suggest a new 2-SD broadcast encryption system using the SS-based technique that was suggested by Jae Hwan Lee et al. in 2014[9]. The new system can reduce the size of ciphertext by 25% of the one in the previous SS-based broadcast encryption system. Also, on a theoretical note, ours is the first 2-SD broadcast encryption system that is provably secure.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.1
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• pp.17-30
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• 2016

In this paper, we propose an efficient public key trace and revoke scheme. An trace and revoke scheme is a broadcast encryption scheme which has a tracing and revocation algorithm. It would maintain security of the scheme to revoke pirate keys which are colluded by malicious users. In addition, property of revocation can be applied to various circumstances because it can help cipher text delivered to certain users who are supposed to. In this paper, we would change the scheme[Augmented broadcast encryption scheme] based on the bilinear groups of the composite order into that of prime order and we can improve the size of public key, secret key, ciphertext considerably. Furthermore, we define property of revocation precisely, so we can obtain the result that the scheme with limited revocation can be expanded to have a full revocation. This paper can be easily applied to the organization such as government, military, which has a hierarchical structure.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.4
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• pp.27-32
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• 2006

Broadcast Encryption allows a center to broadcast encrypted message to a set of users so that only privileged users can decrypt them. In this paper, we propose an efficient broadcast encryption scheme based on the 'Subset Difference' (SD) scheme. It reduces the transmission overhead by 50 percent while the storage overhead remains the same but the computational overhead somewhat increases.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.3
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• pp.400-410
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• 2010

In an identity-based threshold broadcast encryption (IDTHBE) scheme, a broadcaster chooses a set of n recipients and a threshold value t, and the plaintext can be recovered only if at least t receivers cooperate. IDTHBE scheme is different from the standard threshold public key encryption schemes, where the set of receivers and the threshold value are decided from the beginning. This kind of scheme has wide applications in ad hoc networks. Previously proposed IDTHBE schemes have ciphertexts which contain at least n elements. In addition, the security of theses schemes relies on the random oracles. In this paper, we introduce two new constructions of IDTHBE for ad hoc networks. Our first scheme achieves S-size private keys while the modified scheme achieves constant size private keys. Both schemes achieve approximately (n-t)-size ciphertexts. Furthermore, we also show that they are provablesecurity under the decision bilinear Diffie-Hellman Exponent (BDHE) assumption in the standard model.

• Journal of Communications and Networks
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• v.16 no.3
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• pp.258-263
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• 2014

A hierarchical identity-based broadcast encryption (H-IBBE) scheme is an identity-based broadcast encryption (IBBE) scheme in a hierarchical environment. In order to obtain secure H-IBBE schemes in the quantum era, we propose an H-IBBE scheme based on the learning with errors problemassumption.Our scheme achieves indistinguishability from random under adaptive chosen-plaintext and chosen-identity attacks in the random oracle model.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1523-1545
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• 2019

Cloud computing is now a widespread and economical option when data owners need to outsource or share their data. Designing secure and efficient data access control mechanism is one of the most challenging issues in cloud storage service. Anonymous broadcast encryption is a promising solution for its advantages in the respects of computation cost and communication overload. We bring forward an efficient anonymous identity-based broadcast encryption construction combined its application to the data access control mechanism in cloud storage service. The lengths for public parameters, user private key and ciphertext in the proposed scheme are all constant. Compared with the existing schemes, in terms of encrypting and decrypting computation cost, the construction of our scheme is more efficient. Furthermore, the proposed scheme is proved to achieve adaptive security against chosen-ciphertext attack adversaries in the standard model. Therefore, the proposed scheme is feasible for the system of data access control in cloud storage service.