In 2006, Pomykala and Barabasz [Fundamenta Informaticae 69 (2006) 411–425] proposed an elliptic curve based threshold proxy signature scheme which requires shorter cryptographic keys. They claimed that their scheme satisfies the secrecy, the proxy protected, the unforgeability, the non-repudiation, and the known signers. However, in this paper, we show that their scheme cannot achieve the proxy protected, the unforgeability and the non-repudiation by demonstrating a conspiracy attack. In this attack, any t malicious proxy signers can collusively impersonate some other proxy signers to generate proxy signatures.
Tijdschrift beschrijving