Weaknesses and improvements of an efficient certificateless signature scheme without using bilinear pairings

Abstract

The certificateless signature (CLS) scheme is a special signature scheme that solves the key escrow problem in identity-based signature schemes. In CLS schemes, the private key is generated cooperatively by the key generator center (KGC) and signer, such that a malicious KGC cannot masquerade as the signer and sign a message. He et al. in 2011 proposed an efficient CLS scheme without using bilinear pairings. However, we discovered that the CLS scheme by He et al. cannot resist a strong type 2 adversary if this adversary replaces the master public key of the KGC. This work proposes an improved scheme that overcomes this weakness.Sign: When a signer wants to sign a message m, he/she performs the following steps to generate signature (R, s) on message m:Step 1. The signer computesand then sends (m, R, s/ to the verifier.

Further improvement of a certificateless signature scheme without pairing

“…From Table I, we know that the scheme of He et al [21] has better performance than the scheme of Tsai et al and our scheme. However, the scheme of He et al cannot withstand the attack of a Type II adversary [22,23] and is only provably secure against normal adversaries. Although the scheme of Tsai et al has the same performance as our scheme; their scheme is just provably secure against normal adversaries.…”

“…In this section, we will compare the performance of our new scheme with two latest CLS schemes without pairing, that is, the He et al [21] and Tsai et al [23] schemes. Compared with the computational cost of the scale multiplication, the computational cost of hash function operation and modular multiplication operation may be ignored.…”

“…To improve performance, He et al [21] proposed a very efficient CLS scheme without pairings and demonstrated that their scheme is provably secure in the random oracle model. However, Tian and Huang [22] and Tsai et al [23] pointed out that the scheme of He et al is insecure against a Type II adversary who can access the master secret key of the KGC. To improve security, Tsai et al [23] also proposed an improved scheme.…”

“…However, Tian and Huang [22] and Tsai et al [23] pointed out that the scheme of He et al is insecure against a Type II adversary who can access the master secret key of the KGC. To improve security, Tsai et al [23] also proposed an improved scheme. Although the schemes of He et al and Tsai et al are more efficient than other related schemes, both schemes are not real CLS schemes because the user's public key is used by the KGC to generate its partial private key.…”

An efficient certificateless blind signature scheme without bilinear pairing

“…Since groundbreaking work of Al-Riyami and Paterson (2003), many certificateless encryption (CLE) schemes (Sun and Zhang 2010) (Yang and Tan 2011), certificateless signature (CLS) schemes (Tian and Huang 2012) (Tsai et al 2012) (Gong and Li 2012) (He et al 2012c(He et al , 2013a and certificateless key agreement schemes (HE et al 2011c(HE et al , 2012a have been proposed for applications in CLPKC setting. Several certificatless blind signature (CLBS) schemes (Zhang and Zhang 2008) (Wang and Lu 2008) (Yang et al 2009) (Sun and Wen 2009) (Zhang and Gao 2010) (Zhang et al 2011) also were proposed.…”