RE: Signing before Encryption and Signing after Encryption

["Craig Wright" <cwright () bdosyd com au>]

Fairly much.

There are hash based signature schemes for example, but having ones that
may not be repudiated are difficult.

Also comes to good practice. Why sign a message if it may be repudiated
later (though there may be some reasons)?

Craig

-----Original Message-----
From: Gregory Rubin [mailto:grrubin () gmail com]
Sent: 25 March 2006 7:15
To: Craig Wright
Cc: gillettdavid () fhda edu; shyaam () gmail com;
security-basics () securityfocus com
Subject: Re: Signing before Encryption and Signing after Encryption

So it sounds to me that this is more a legal and contractual issue than
a technical issue, or am I misreading this?

Greg Rubin

On 3/22/06, Craig Wright <cwright () bdosyd com au> wrote:
> 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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