  In [3] the authors proposed a new aggregate signature scheme referred to as
multiple-TA (trusted authority) one-time identity-based aggregate signature
(MTA-OTIBAS). Further, they gave a concrete MTA-OTIBAS scheme. We recall here
the definition of MTA-OTIBAS and the concrete proposed scheme. Then we prove
that our MTA-OTIBAS concrete scheme is existentially unforgeable against
adaptively chosen-message attacks in the random oracle model under the co-CDH
problem assumption.
