The European Union Electronic Signature Directive of January, 2000,
defines an advanced electronic signature. This signature must meet
all of the following requirements except that:

A.
It must be created using means that are generally accessible and
available.

B.
It must be uniquely linked to the signatory.

C.
It must be linked to the data to which it relates in such a manner that
any subsequent change of the data is detectable.

D.
It must be capable of identifying the signatory.

Explanation:
The Directive requires that the means be maintained under the sole
control of the signatory. This requirement is a particularly difficult
one to achieve. One approach is to use different tokens or smart cards
for the different transactions involved. The other answers are typical
characteristics of digital signatures that can be implemented with
public key cryptography.