A ring signature is an anonymous signature that implements both the authentication of the message and the anonymity of the signer. In a ''normal'' ring signature scheme, the same signer can generate multiple ring signatures, but the verifier cannot find this fact. Linkable ring signature (LRS) solves the problem. In the setting, the identity of the signer is still anonymous, and if the same signer generates multiple ring signatures, the verifier can confirm the fact. Linkable ring signatures are applied to some actual scenarios, such as e-cash, e-voting and ad-hoc network authentication. In this paper, we presented a new identity-based linkable ring signature scheme that avoids certificate management. We then gave the security proofs in the random oracle model (ROM) and compared the efficiency of it with the previous schemes. The new scheme requires only 7 pairing operations in signing and verifying. It is the most efficient linkable ring signature in the identity-based setting. INDEX TERMS Identity-based cryptography, ring signature, linkable, pairing, random oracle model.

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Blind signature is a special type of digital signature, the signer cannot see the specific content signed. However, blindness may cause users to abuse their rights. Partial blind signature allows the signer to embed pre-negotiated public information in the blind signature without losing blindness, which can prevent users from abusing their rights. Islam et al. [10] presented an identity-based partial blind signature scheme and claimed that it is provable secure. However, in this paper we proved that the scheme [10] is vulnerable against the tampering attacks with public information. We then proposed a new identity-based partial blind signature scheme, showed the security proofs under the assumption that the elliptic curve discrete logarithm problem (ECDLP) is difficult. The new scheme does not use pairing operations and enjoys less computation cost.