Browsing by Author "Yeh, Yi-Shiung"

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A DL Based Short Strong Designated Verifier Signature Scheme with Low Computation
(2011-03-01)
Lin, Han-Yu
;
Wu, Tzong-Sun
;
Yeh, Yi-Shiung
;
資訊工程學系
;
Department of Computer Science
A designated verifier signature (DVS) scheme is a special type of digital signature scheme without the property of non-repudiation. Such schemes only allow the designated verifier to validate the signer's signature. Meanwhile, the designated verifier is not able to convince any third party of the signature's actual signer, since he can also generate a computationally indistinguishable one compared to the received signature. A strong designated verifier signature (SDVS) scheme further prohibits anyone except for the intended verifier from validating the signature as it requires the designated verifier's private key to finish the verification process. In this paper, we propose an efficient short SDVS scheme with low computation costs. Unlike many SDVS schemes primarily implemented on pairing-based cryptosystems, we focus on the discrete logarithms (DL) based system. Compared with those DL based SDVS schemes, ours provides better functionalities and efficiency and hence benefits the practical applications. In addition, the security requirement of unforgeability against existential forgery on adaptive chosen-message attacks (EU-CMA) is proved in the random oracle model.
A TRANSPOSITIONAL ADVANCED ENCRYPTION STANDARD (AES) RESISTS 3-ROUND SQUARE ATTACK
(2009-05-01)
Yeh, Yi-Shiung
;
Lee, Chen-Yu
;
Huang, Ting-Yu
;
Lin, Chu-Hsing
;
資訊工程學系
In this paper, an advanced encryption standard (AES) variant is proposed that is resistant to linear cryptanalysis, differential cryptanalysis, and the square attack. We replace some procedures in the round function of AES and take the bit as the operation unit to foil the square attack. Also, we apply linear cryptanalysis and differential cryptanalysis to the proposed cipher. The proposed cipher is shown to be superior to AES in many aspects.
Design of proxy signature in the Digital Signature Algorithm (DSA)
(2006-07-01)
Chen, I-Te
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Chang, Ming-Hsin
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Yeh, Yi-Shiung
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資訊工程學系
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Department of Computer Science
The use of proxy signature has attracted considerable attention and has been deployed in many applications. Unfortunately, most of the proxy signature schemes, which have been proposed up to now, are not based on standard signature such as Digital Signature Algorithm (DSA). Consequently, those proposals have inevitably been considered infeasible because of obvious security weaknesses so they suffer from new attacks. In fact, with the application of standard signature like DSA, which has been fully discussed, a proxy signature scheme could be well accepted for the deployment in many applications. Therefore, we propose a new proxy signature scheme which combines the DSA properties with proxy signatures. In other words, our scheme keeps not only the properties of the DSA but also fulfills the requirements of proxy signatures. We hope our new proxy signature based on DSA combining Public-key infrastructure (PKI) mechanism could be used in practice as well as the conventional DSA.
Efficient proxy signcryption scheme with provable CCA and CMA security
(2010-10-01)
Lin, Han-Yu
;
Wu, Tzong-Sun
;
Huang, Shih-Kun
;
Yeh, Yi-Shiung
;
資訊工程學系
For facilitating the confidential transaction with delegation such as on-line proxy auction and business contract signing by an authorized proxy, we propose an efficient proxy signcryption scheme from pairings. Our scheme allows an original signer to delegate his signing power to a proxy one such that the latter can signcrypt a plaintext on behalf of the former. The signcrypted message can only be decrypted by a designated recipient who is also responsible for verifying the recovered proxy signature. To deal with a later dispute over repudiation, the designated recipient can easily announce the ordinary proxy signature for public verification without extra computational efforts. To guarantee the realistic applicability, we demonstrate that our scheme outperforms previous works in terms of functionalities and computational efficiency. Moreover, the security requirement of confidentiality against indistinguishability under adaptive chosen-ciphertext attacks (IND-CCA2) and that of unforgeability against existential forgery under adaptive chosen-message attacks (EF-CMA) are proved in random oracle models. (C) 2010 Elsevier Ltd. All rights reserved.
Efficient proxy signcryption scheme with provable CCA and CMA security
(2010-10-01)
Lin, Han-Yu
;
Wu, Tzong-Sun
;
Huang, Shih-Kun
;
Yeh, Yi-Shiung
;
資訊工程學系
For facilitating the confidential transaction with delegation such as on-line proxy auction and business contract signing by an authorized proxy, we propose an efficient proxy signcryption scheme from pairings. Our scheme allows an original signer to delegate his signing power to a proxy one such that the latter can signcrypt a plaintext on behalf of the former. The signcrypted message can only be decrypted by a designated recipient who is also responsible for verifying the recovered proxy signature. To deal with a later dispute over repudiation, the designated recipient can easily announce the ordinary proxy signature for public verification without extra computational efforts. To guarantee the realistic applicability, we demonstrate that our scheme outperforms previous works in terms of functionalities and computational efficiency. Moreover, the security requirement of confidentiality against indistinguishability under adaptive chosen-ciphertext attacks (IND-CCA2) and that of unforgeability against existential forgery under adaptive chosen-message attacks (EF-CMA) are proved in random oracle models. (C) 2010 Elsevier Ltd. All rights reserved.
Finding Near-Optimum Message Scheduling Settings for SHA-256 Variants Using Genetic Algorithms
(2013-09-01)
Lin, Chu-Hsing
;
Lee, Chen-Yu
;
Kavi, Krishna M.
;
Chen, Deng-Jyi
;
Yeh, Yi-Shiung
One-way hash functions play an important role in modem cryptography. Matusiewicz et al. proved that the message scheduling is essential for the security of SHA-256 by showing that it is possible to find collisions with complexity 2(64) hash operations for a variant without it. In this article, we first proposed the conjecture that message scheduling of SHA algorithm has higher security complexity (or fitness value in Genetic algorithm) if each message word (W-t) involves more message blocks (M-i) in each round. We found some evidence supports the conjecture. Consider the security of SHA-0 and SHA-1. Since Chabaud and Joux shown that SHA-1 is more secure than SHA-0. Further, Wang found collisions in full SHA-0 and SHA-1 hash operations with complexities less than 2(39) and 2(69), respectively. We found it is consistent from the viewpoint of message blocks (terms) involved in each message word. It clearly shown that the number of terms involved in SHA-1 is more than that in SHA-0, taking W-27 as an example, 14 and 6, respectively. Based on the conjecture we proposed a new view of complexity for SHA-256-XOR functions, a variant of SHA-256, by counting the terms involved in each equation, instead of analyzing the probability of finding collisions within SHA-256-XOR hash function. Our experiments shown that the parameter set in each equation of message schedule is crucial to security fitness. We applied genetic algorithms to find the near-optimal message schedule parameter sets that enhance the complexity 4 times for SHA-1 and 1.5 times for SHA-256-XOR, respectively, when compared to original SHA-1 and SHA-256-XOR functions. The analysis would be interesting for designers on the security of modular-addition-free hash function which is good for hardware implementation with lower gate count. And the found message schedule parameter sets would be a good reference for further improvement of SHA functions.
Self-Certified Proxy Convertible Authenticated Encryption Scheme
(2008)
Lin, Han-Yu
;
Wu, Tzong-Sun
;
Huan, Ting-Yu
;
Yeh, Yi-Shiung
;
資訊工程學系
A proxy convertible authenticated encryption (CAE) scheme allows an original signer to delegate his signing power to a proxy signer such that the proxy signer can generate an authenticated ciphertext on behalf of the original signer The generated authenticated ciphertext can only be decrypted and verified by the specific recipient instead of everyone else for the purpose of confidentiality. Integrating with self-certified public key systems, the proposed scheme can save more communication overheads and computation efforts, since it is not necessary to transmit and verify the public key certificate. That is, authenticating the public key can be combined with subsequent cryptographic operations such as the signature verification. In case of a later repudiation, the specific recipient has the ability to convert the signature into an ordinary one for convincing anyone of the signer dishonesty.
Structural Binary CBC Encryption Mode
(2009-05-01)
Yeh, Yi-Shiung
;
Huang, Ting-Yu
;
Lin, Han-Yu
;
資訊工程學系
;
Department of Computer Science
A block cipher is a kind of symmetric encryption algorithm that operates on blocks of fixed length, often 64 or 128 bits. It transforms blocks of plaintext into blocks of ciphertext of the same length under the provided secret key. A common characteristic of currently Widely used modes of operation such as CBC, CFB and OFB is the sequential procedure. i.e., the encryption/decryption algorithm can not start to process until the previous operation finished, which is considered to be inefficient in multi-processor structures. In this paper, we combine CBC mode of operation and the binary free data structure to propose a new structural binary CBC encryption mode allowing parallelized computing. A significant property of the proposed mode of operation is independent branch operations. When applied in multi-processor structures, different branch operations can make effective use of CPUs to perform in parallel, which will lead to shorter computing time and greatly improve the overall performance.
Untraceable Identity Management Framework for Mobile Access
(2008)
Kao, Min-Chih
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Yeh, Yi-Shiung
;
Wang, Chuan-Chi
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資訊工程學系
;
Department of Computer Science
Although some Extensible Authentication Protocol (EAP) methods such as EAP-TTLS (Tunneled Transport Layer Security) can hide true identity to protect the privacy of the mobile user, they cannot identify the mobile user for accounting and authorization purposes. The EAP framework lacks a mechanism to manage the relationship between true identities and pseudo identities. This study proposes an identity management framework based on the short-lived certificate so that the proposed scheme can deal with both authentication and authorization with privacy. The proposed scheme has no need of a certificate revoke scheme in which the authentication process can only occur between the mobile user and an authenticator. This greatly reduces the authentication delay. Thus, the proposed scheme can achieve both privacy and efficiency.