• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.5
• /
• pp.2792-2810
• /
• 2017

Forward-secure signature is a specific type of signature, which can mitigate the damage caused by the signing key exposure. Most of the existing forward-secure (identity-based) signature schemes can update users' secret keys at each time period, achieve the existential unforgeability, and resist against classical computer attacks. In this paper, we first revisit the framework of forward-secure identity-based signatures, and aim at supporting flexible key update at multi time period. Then we propose a post-quantum forward-secure identity-based signature scheme from lattices and use the basis delegation technique to provide flexible key update. Finally, we prove that the proposed scheme is strongly unforgeable under the short integer solution (SIS) hardness assumption in the random oracle model.

• Convergence Security Journal
• /
• v.21 no.1
• /
• pp.33-44
• /
• 2021

Data outsourcing utilizing the Cloud faces a problem of the third-party exposure, modulation, and reliability for the provided computational delegation results. In order to solve those problematic security issues, homomorphic encryption(HE) which executes calculation and analysis on encrypted data becomes popular. By extension, a new type of HE with a authentication functionality, homomorphic authenticated encryption(HAE) is suggested. However, a research on the HAE is on the initial stage. Furthermore, based on a message authenticated scheme with HE, the method and analysis to design is still absent. This paper aims to analyze an HAE, with a generic combination of a message authenticated scheme and a HE, known as "Encrypt with Authentication". Following a series of analysis, we show that by adopting a unforgeable message authenticated scheme, the generically constructed HAE demonstrated an unforgeability as well. Though, a strong unforgeability is not the case. This paper concludes that although indistinguishable HE can be applied to design the HAE, a security issue on the possibility of indistinguishability is still not satisfied.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.7 no.12
• /
• pp.3261-3273
• /
• 2013

In the paper, we propose a novel adaptively secure hierarchical identity-based signature scheme from lattices. The size of signatures in our scheme is shortest among the existing hierarchical identity-based signature schemes from lattices. Our scheme is motivated by Gentry et al.'s signature scheme and Agrawal et al.'s hierarchical identity-based encryption scheme.

• ETRI Journal
• /
• v.34 no.2
• /
• pp.235-244
• /
• 2012

An identity-based strong designated verifier signature scheme provides restricted verifiability only for a verifier designated by a signer and proper privacy for the signer. In this paper, we show that strong designated verifier signature schemes do not satisfy the self-unverifiability requirement in the sense that not only exposure of the verifier's secret key but also of the signer's secret key enables an attacker to verify signatures, which should have been the exclusive right of the verifier. We also present a generic method to construct a strong identity-based designated verifier signature scheme with self-unverifiability from identity-based key encapsulation and identity-based key sharing schemes. We prove that a scheme constructed from our method achieves unforgeability, non-transferability, and self-unverifiability if the two underlying components are secure. To show the advantage of our method, we present an example that outputs short signatures and we analyze its performance.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.24 no.3
• /
• pp.461-475
• /
• 2014

Homomorphic MAC is a cryptographic primitive which protects authenticity of data, while allowing homomorphic evaluation of such protected data. In this paper, we present a new homomorphic MAC, which is based on integers, relying only on the existence of secure PRFs, and having efficiency comparable to the practical Catalano-Fiore homomorphic MAC. Our scheme is unforgeable even when MAC verification queries are allowed to the adversary, and we achieve this by showing strong unforgeability of our scheme.

• Journal of applied mathematics & informatics
• /
• v.31 no.3_4
• /
• pp.425-441
• /
• 2013

In literature, several strong designated verifier signature (SDVS) schemes have been devised using elliptic curve bilinear pairing and map-topoint (MTP) hash function. The bilinear pairing requires a super-singular elliptic curve group having large number of elements and the relative computation cost of it is approximately two to three times higher than that of elliptic curve point multiplication, which indicates that bilinear pairing is an expensive operation. Moreover, the MTP function, which maps a user identity into an elliptic curve point, is more expensive than an elliptic curve scalar point multiplication. Hence, the SDVS schemes from bilinear pairing and MTP hash function are not efficient in real environments. Thus, a cost-efficient SDVS scheme using elliptic curve cryptography with pairingfree operation is proposed in this paper that instead of MTP hash function uses a general cryptographic hash function. The security analysis shows that our scheme is secure in the random oracle model with the hardness assumption of CDH problem. In addition, the formal security validation of the proposed scheme is done using AVISPA tool (Automated Validation of Internet Security Protocols and Applications) that demonstrated that our scheme is unforgeable against passive and active attacks. Our scheme also satisfies the different properties of an SDVS scheme including strongness, source hiding, non-transferability and unforgeability. The comparison of our scheme with others are given, which shows that it outperforms in terms of security, computation cost and bandwidth requirement.

• The Journal of the Korea Contents Association
• /
• v.11 no.1
• /
• pp.42-49
• /
• 2011

Proxy signature schemes are configured as proxy signers on behalf of their original signers can be allowed to sign messages. Basic security requirements of proxy signature schemes include the strong unforgeability and the verifiability of delegation. So far, a variety of proxy signature schemes that proved on individual basic security terms but not proved on compounded security terms are proposed. Especially the proposed proxy signature schemes based on RSA problem are proved vulnerable to an attacker with his own private key in terms of the impersonating attack. A unauthorized attacker can generate the proxy signature without the appointee's consent or authorization. In this paper, we propose a proxy signature scheme based on RSA problems and warrants that can be proved the security against the impersonating attack. The proposed proxy signature scheme is analyzed on the safety and compared in terms of efficiency with other proxy signature schemes.