Proxy signature schemes allow a proxy signer to generate a proxy signature
on behalf of an original signer. However, since in previous proxy signature
schemes a proxy signature is created on behalf of only one original signer
, these schemes are referred to as proxy mono-signature schemes. A new type
of proxy signature scheme is presented called the proxy multi-signature sc
heme in which a proxy signer can generate a proxy signature on behalf of tw
o or more original signers.