Anna Lysyanskaya Silvio Micali Leonid Reyzin Hovav Shacham Sequential Aggregate Signatures from Trapdoor Permutations. 91 2003 2003 IACR Cryptology ePrint Archive http://eprint.iacr.org/2003/091 db/journals/iacr/iacr2003.html#LysyanskayaMRS03