Cryptography Reference
In-Depth Information
Figure 4.6
The scene at the courtroom during evaluation of signed documents. From Birgit
Pfitzmann,
Digital Signature Schemes: General Framework and Fail-Stop Signatures
(Berlin: Springer, 1996), 13. Used by permission.
and that the document has not been modified since the signature's
creation (data integrity).
Non-repudiation has subsequently migrated back from the standardiza-
tion universe into the scientific cryptography literature. To the three objec-
tives of historical concern to the discipline—confidentiality, data integrity,
and authentication—the
Handbook of Applied Cryptography
adds a fourth,
non-repudiation, defined as “a service which prevents an entity from
denying previous commitments or actions.”
26
This is an ambitious goal.
Legal scholar Jane Winn humorously notes, “As anyone with children
knows, you cannot prevent someone from 'falsely denying' an action.”
27
Nevertheless, it is under the umbrella of non-repudiation that cryptogra-
phy has staked a claim as a forensic science essential to the network society.
Attacks and Adversaries
To these security services, cryptographers would add a taxonomy of
attacks
,
a taxonomy that models an adversary's resources as he tries to break the
system and defeat the security properties of signatures. That is, if signatures
provide authentication, then a corresponding threat is the ability for an
