Do Symmetric Key Algorithms provide authenticity?

Date sent: Sat, 08 Jul 2006 19:17:33 +0000
From: Rabbani <smrabbaniyahoo.com>

&gt; Symmetric key algorithms can provide confidentiality but not
> authentication, says Shon Harris in her book, All In One CISSP exam
> guide (Page # 680, Quick Tips, Cryptography).
>
> Whereas the SYBEX book, CISSP Study guide, by James, Ed and Mike
> says 'Authentication can be achieved by both symmetric and asymmetric
> cryptosystems.

Limited authentication, as in detection of changes by errors or an adversary, can
be detected by both, but only if both parties to the communication are honest.
Non-repudiation can only be achieved by asymmetric.

(And, of course, there are always provisos like "man-in-the-middle".)

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