  It has recently been shown that, contrarily to a common belief, money
transfer in the presence of faulty (Byzantine) processes does not require
strong agreement such as consensus. This article goes one step further: namely,
it first proposes a non-sequential specification of the money-transfer object,
and then presents a generic algorithm based on a simple FIFO order between each
pair of processes that implements it. The genericity dimension lies in the
underlying reliable broadcast abstraction which must be suited to the
appropriate failure model. Interestingly, whatever the failure model, the money
transfer algorithm only requires adding a single sequence number to its
messages as control information. Moreover, as a side effect of the proposed
algorithm, it follows that money transfer is a weaker problem than the
construction of a safe/regular/atomic read/write register in the asynchronous
message-passing crash-prone model.
