• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.4
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• pp.105-114
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• 2009

Messages exchanged among vehicles must be authenticated in order to provide collision avoidance and cooperative driving services in VANET. However, digitally signing the messages can violate the privacy of users. Therefore, we require authentication systems that can provide conditional anonymity. Recently, Zhang et al. proposed conditionally anonymous authentication system for VANET using tamper-resistant hardware. In their system, vehicles can generate identity-based public keys by themselves and use them to sign messages. Moreover, they use batch verification to effectively verify signed messages. In this paper, we provide amelioration to Zhang et al.'s system in the following respects. First, we use a more efficient probabilistic signature scheme. Second, unlike Zhang et al., we use a security proven batch verification scheme. We also provide effective solutions for key revocation and anonymity revocation problems.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.1
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• pp.101-111
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• 2004

Preneel, Govaerts, and Vandewalle considered the 64 basic ways to construct a collision resistant hash function from a block cipher. They regarded 12 of these 64 schemes as secure, though no proofs or formal claims were given. Black, Rogaway, and Shrimpton presented a more proof-centric look at the schemes from PGV. They proved that, in the black box model of block cipher, 12 of 64 compression functions are CRHFs and 20 of 64 extended hash functions are CRHFs. In this paper, we present 64 schemes of block-cipher-based universal one way hash functions using the main idea of PGV and analyze these schemes in the black box model. We will show that 30 of 64 compression function families UOWHF and 42 of 64 extended hash function families are UOWHF. One of the important results is that, in this black box model, we don't need the mask keys for the security of UOWHF in contrast with the results in general security model of UOWHF. Our results also support the assertion that building an efficient and secure UOWHF is easier than building an efficient and secure CRHF.