Forward-secure multisignature and blind signature schemes

A blind signature enables a user to obtain signatures on any message from an authority who cannot acquire any information on the message being signed. A blind ring signature scheme is designed as a ring signature scheme with the blindness property. The scheme allows any member of a group anonymously sign a message on behalf of the group. Also, the user with the message can blind it before transmitting to the group. At Asiacrypt 2010, Rückert constructed the first blind signature scheme using ideal lattices. Recently, Zhang, Jiang and Zheng, and Alkadri, Bansarkhani and Buchmann proposed two improved blind signature schemes based on the SIS problem and the Ring SIS problem in 2018 and 2020, respectively. At WISA 2019, motivated by these blind signature schemes, Le, Duong and Susilo constructed the first lattice-based blind ring signature scheme provably secure under the hardness assumption of the SIS problem in random oracle model. In this paper, we show that Rückert’s scheme, Alkadri-Bansarkhani-Buchmann scheme and Zhang-Jiang-Zheng scheme, and Le-Duong-Susilo scheme do not achieve blindness, i.e. the signer can link a valid message-signature pair after interacting with various users. We show that the cause of vulnerabilities of the blind schemes is that the blinding factors to hide real messages being signed are exposed by specific algebraic relations in the underlying rings. To hide the blinding factors, we use homomorphic encryption schemes. Finally, we propose a generic construction from a semantically secure homomorphic encryption scheme and a one-more unforgeable blind signature scheme that does not achieve blindness to a new blind signature scheme that achieves blindness as well as one-more unforgeability.

An efficient provably secure identity-based blind signature (IBBS) scheme based on bilinear pairings is proposed. Assuming the intractability of the q-Strong Diffie-Hellman problem, our IBBS is unforgeable under adaptive chosen-message and ID attack. Because of avoiding using the inefficient MapToPoint function, our IBBS can offer advantages in runtime over the schemes available. Based on this ID-based blind signature scheme, we describe the first ID-based threshold blind signature (TBS) and show that it has security properties of unforgeability and robustness.

Forward-secure signatures are proposed to tackle the key exposure problem , in which the security of all signatures prior to key leakage is still kept even if the secret key leaks. In this paper, we construct two forward-secure multisignature schemes, one forward-secure threshold signature scheme, and one forward-secure blind signature scheme. Our constructions are based on the recently proposed forward-secure signature scheme from bilinear maps in [11]. Our constructions are very efficient and useful thanks to the elegant structure of the base scheme. Such schemes play an important role in many electronic applications such as cryptographic election systems , digital cash schem es, and e-cheques.

An efficient provably secure identity-based blind signature (IBBS) scheme based on bilinear pairings is proposed. Assuming the intractability of the q-Strong Diffie-Hellman problem, our IBBS is unforgeable under adaptive chosen-message and ID attack. Because of avoiding using the inefficient MapToPoint function, our IBBS can offer advantages in runtime over the schemes available. Based on this ID-based blind signature scheme, we describe the first ID-based threshold blind signature (TBS) and show that it has security properties of unforgeability and robustness.

Blind signature is an interesting cryptographic primitive which allows user to get signature on his document from signatory authority, without leaking any information. Blind signature is useful in many e-commerce applications where user’s anonymity is the main concern. Since the Zhang et al., was the first to propose the identity based blind signature, many schemes based on bilinear pairing have been proposed. But the computational cost of pairing operation on elliptic curve is around 20 times the point multiplication on an elliptic curve. In order to save the running time, we present a new Identity-Based Blind Signature (ID-BS) scheme whose security is based on elliptic curve discrete logarithm problem (ECDLP). Performance comparison shows that proposed scheme reduces the cost of computation. Security analysis shows that proposed scheme is secure against the adversary and achieves the property of blindness and Non-forgeabillity. At the end; we propose an e-cash payment system based on our ID-based blind signature scheme.

Blind signatures, introduced by Chaum, allow a user to obtain a signature on a message without revealing any thing about the message to the signer. Blind signatures play an important role in plenty of applications such as e-voting, e-cash system where anonymity is of great concern. Identity based(ID-based) public key cryptography can be a good alternative for certificate based public key setting, especially when efficient key management and moderate security are required. In this paper, we propose an ID-based blind signature scheme from bilinear pairings. The proposed scheme is based on the Hess ID- based digital signature scheme. Also we analyze security and efficiency of the proposed scheme.

Universal forgery attacks and selected forgery attacks on both weak and strong blind signature schemes based on Elgamal signature equation proposed by Wang et al. are developed. Without using any secret key, anyone can forge a valid signature through selecting some random parameters. The possibility of forging the blind schemes is analyzed and moreover, an improved weak blind signature scheme and an improved strong blind signature scheme are designed. Also, the securities of the improved blind signatures are analyzed.

In order to solve the problem of computational complexity brought by bilinear pairing in identity based blind signature, a new ID-based blind signature scheme is proposed combined with Elgamal algorithm, and the blind signature scheme is applied to the field of civil aviation data transmission firstly. The signer is not visible to the original message and can't restore the original message by the signed message. The use of hash function to deal with both private key and the identity information is secure under the Random Oracle Model. Based on the classical Elgamal algorithm, the problem belongs to the discrete logarithm problem. The scheme is applied to the field of civil aviation data transmission and the experimental results show that it can effectively resist key recovery attacks and signature forgery attacks. The scheme has strong anti-attack ability and effective operation ability. Compared with other schemes, it needs less module operation and exponential operation. To sum up, this scheme is better than other schemes in the civil aviation's field.

As a variation of ordinary digital signature scheme, a proxy signature scheme enables a proxy signer to sign messages on behalf of the original signer. Proxy multi-signature is an extension of the basic proxy signature primitive, and permits two or more entities to delegate their signing capabilities to some other entity. Many identity-based proxy multi signature (IBPMS) schemes using bilinear pairings have been proposed. But the relative computation cost of the pairing is approximately more than ten times of the scalar multiplication over elliptic curve group. In order to save the running time and the size of the signature, in this paper, we propose an IBPMS scheme without bilinear pairings. We also prove the security of our scheme against adaptive chosen message attack under random oracle model. With the running time being saved greatly, our scheme is more applicable than the previous related schemes for practical applications.KeywordsDigital signatureIdentity-based cryptographyProxy-multi signatureElliptic curve discrete log problem

Optimal resilient threshold GQ signatures

In this paper, we motivate the need for efficient multisignature schemes in delegated mobile services. With the schemes, delegates can be identified and delegated accesses can be controlled. First, we give a new digital signature scheme with message recovery. Based on the digital signature scheme, two digital multisignature schemes are proposed: the parallel multisignature scheme and the serial multisignature scheme. The parallel multisignature scheme allows each user to sign the same message separately and independently, and then combines all individual signatures into a multisignature. The serial multisignature scheme allows a group of users to sign the message serially, and does not need to predetermine the signing order. Both multisignature schemes can withstand the attacks that aim to forge the signatures or to get the private keys of the signers.

In this paper, we describe efficient forgery and full-key recovery attacks on the ℓ-IC− signature scheme recently proposed at PKC 2007. This cryptosystem is a multivariate scheme based on a new internal quadratic primitive which avoids some drawbacks of previous multivariate schemes: the scheme is extremely fast since it requires one exponentiation in a finite field of medium size and the public key is shorter than in many multivariate signature schemes. Our attacks rely on the recent cryptanalytic tool developed by Dubois et al. against the SFLASH signature scheme. However, the final stage of the attacks requires the use of Gröbner basis techniques to conclude to actually forge a signature (resp. to recover the secret key). For the forgery attack, this is due to the fact that Patarin’s attack is much more difficult to mount against ℓ-IC. The key recovery attack is also very efficient since it is faster to recover equivalent secret keys than to forge.KeywordsSignature SchemeTotal BreakForgery AttackBilinear EquationTrivial RelationThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

This paper presents two Identity-Based Blind Signature (IBBS) schemes based on bilinear pairings. Both of them enjoy the following features. First, they achieve the optimal bound of round complexity for blind signatures,i.e., each signature can be blindly generated with one round (or two moves) of message exchanges between the signature requesting user and signer. Second, their security is proved without the ROS assumption, which assumes that it is infeasible to find an overdetermined, solvable system of linear equations modulo q with random inhomogenities. Due to this reason, the order of underlying group does not need to be very large any more, as compared to the previous work. Third, the key extraction algorithm used is the most popular one in ID-based cryptography. In fact, the proposed two constructions are first IBBS schemes enjoying all the above advantages. Different from other IBBS schemes, these two IBBS schemes are constructed from scratch in the sense that new ID-based signature schemes are customized and new assumptions (e.g., two versions of one-more bilinear Diffie- Hellman inversion assumption) are formalized.We also show that the new ID-based schemes and new assumptions may have other interesting applications.

Randomization enhanced Chaum's blind signature scheme

In this paper, we first propose an efficient provably secure identity-based signature (IBS) scheme based on bilinear pairings, then propose an efficient identity-based blind signature (IBBS) scheme based on our IBS scheme. Assuming the intractability of the Computational Diffie-Hellman Problem, our IBS scheme is unforgeable under adaptive chosen-message and ID attack. Efficiency analyses show that our schemes can offer advantages in runtime over the schemes available. Furthermore, we show that, contrary to the authors claimed, Zhang and Kim’s scheme in ACISP 2003 is one-more forgeable, if the ROS-problem is solvable.