Hi David,
Non-repudiation has different requirements in different legal
jurisdictions.
There needs to be a manner to verify the keys (i.e. PKI). I can get a
verisign certificate calling myself Bill Gates. This does not mean for
the purpose of legal contractual negotiations that I am Bill Gates. I
could sign an email as such though.
For non-repudiation to work, there needs to be an attestation by the
operator of the certificate authority.
The following are some guidelines for non-repudiation, based on locality
of course:
Australia National Electronic Authentication Council,
Liability and other Legal Issues in the Use of PKI
Digital Certificates (May 2002).
EC, Directive 1999/93/EC of the European Parliament and of
the Council
Austria, Signature Law, 2000
England, Scotland and Wales
Electronic Communications Act, 2000
Germany Signature Law, 2001
Sweden Qualified Electronic Signatures Act (SFS 2000:832) (in swedish).
India Information Technology Act, 2000
New Zealand Electronic Transactions Act, 2003 sections 22-24
USA Electronic Signatures in Global and National Commerce
Act (E-SIGN),
at 15 U.S.C. 7001 et seq
Switzerland Federal Law on Certification Services Concerning the
Electronic Signature, 2003
To take a quote from the English Ministry associated with Digital
Signature law:
"A private key authenticated by a digital certificate generated within a
PKI can be considered as the electronic equivalent of a passport. Both
establish identities for persons who have met the requisite identity
checks. The community accepts the validity of the holder's identity
because it trusts the issuer. The identity can be used to authenticate
the holder in subsequent transactions without directly involving the
issuer."
Web of trust models such as PGP can result in a signature, but the issue
of non-repudiation is not fulfilled in that the issuer can not be held
to account separately (as it is a self signed certificate).
In situations where the parties have had prior dealings, it may be
possible to verify the owner of the public key, for example, at a
personal meeting, parties may exchange public keys on floppy disks (eg
key signing parties). However, if the parties are unknown to each other,
and perhaps in different jurisdictions, the requisite level of
confidence is not present. The solution to this lies in the public key
infrastructure and is governed by different levels of trust.
Regards
Craig
-----Original Message-----
From: David Gillett [mailto:gillettdavid@fhda.edu]
Sent: 23 March 2006 8:24
To: Craig Wright; shyaam@gmail.com; security-basics@securityfocus.com
Subject: RE: Signing before Encryption and Signing after Encryption
Does non-repudiation require anything more than assurance that the
private key (a) MUST have been used, and (b) HASN'T been compromised?
Are you just alluding to the measures which support those assertions, or
to some additional requirement(s) that escapes me?
[If your private key isn't really private, all bets are off.]
David Gillett
-----Original Message-----
From: Craig Wright [mailto:cwright@bdosyd.com.au]
Sent: Wednesday, March 22, 2006 12:56 PM
To: gillettdavid@fhda.edu; shyaam@gmail.com;
security-basics@securityfocus.com
Subject: RE: Signing before Encryption and Signing after Encryption
True, but the argument was not one as to which is the better method.
There are several secure hashing algorithms.
Further there is more to verification to source than just asymmetric
keys. Non-repudiation is a complex field in itself and requires a
entire range of associated infrastructure.
Regards
Craig
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