Cryptanalysis and improvement of two ring signature schemes provably secure in standard model
Sun Yan-fei · Journal of Communications · 2008
The security of the two ring signature schemes proposed by Au(2006) and Chow(2006) was analyzed, and it's found that both the ring signature schemes were susceptible to multiple-known-signature existential forgery or group-changing attack. To guard against the two attacks, the two ring signature schemes were improved, which can make the improved schemes were still secure even in the stronger security model.