  The purpose of incremental cryptography is to allow the updating of
cryptographic forms of documents undergoing modifications, more efficiently
than if we had to recompute them from scratch. This paper defines a framework
for using securely a variant of the incremental hash function designed by
Bok-Min Goi et al. The condition of use of their hash function is somehow
impractical since they assume that the blocks of the message are all distinct.
In this paper we show how we can discard this strong assumption so as to
construct the first practical incremental asymmetric signature scheme that
keeps efficient update operations. Finally, as the proposed scheme has the
defect to severely expand the signature size, we propose a solution which
drastically reduces this drawback.
