Analysis of frame attack on Hsu et al.’s non-repudiable threshold multi-proxy multi-signature scheme with shared verification

Tzeng et al. proposed a threshold multi-proxy multi-signature scheme with threshold verification. Recently, Hsu et al. pointed out that Tzeng et al.’s scheme was vulnerable to insider attacks and proposed an improvement to eliminate the pointed out security leak. We will show that Hsu et al.’s improvement cannot resist the frame attack. That is, after intercepting a valid proxy signature, an adversary can change the original signers to himself, and forge a proxy signature. To remedy this weakness, we will propose a new method.