4. A method of automatically adapting, without human intervention, reference signatures to changing writing styles of a signer in a signature verification system, comprising the steps of: (a) creating a second set of reference signatures which contain current sample signatures indicating current signing characteristics; (b) comparing a sample signature to each signature in a first set of reference signatures; (c) accepting the sample signature if it would be accepted as a valid signature when compared with any of the signatures in the first set of reference signatures; (d) comparing a sample signature to each signature in the second set of reference signatures if the sample signature would not have been accepted as valid when compared with any of the signatures in the first set of reference signatures and which is close to one of the signatures in the first set of reference signatures, the sample signature being accepted as a valid signature if it is accepted when compared to any of the signatures in the second set of reference signatures, (e) changing the reference signatures in the second set of reference signatures if the sample signature is accepted as valid when compared with signatures in the first set of reference signatures as in step (c), and changing the reference signatures in the first set of reference signatures if the sample signature is accepted as valid when compared with signatures in the second set of reference signatures as in step (d).
5. A method as recited in claim 4, wherein the oldest signatures in the second set of reference signatures are updated with accepted signatures and with signatures which are close and which are obtained during a signature verification session which session includes an accepted signature.