Re: [CISSP-D] Do Symmetric Key Algorithms provide authenticity?

On 8 Jul 2006 at 19:17, Rabbani wrote:

> 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.
>
> Can any CISSPs advise on this.

  In an asymmetric key cryptosystem, each entity has its own private key 
which need never be shared, transmitted, or made available.  So successful 
participation in the cryptosystem implicitly authenticates each entity as 
the possessor of its unique private key.

  In a symmetric cryptosystem, a shared key must be distributed to all 
entities, with attendant risk that the key distribution process might get 
compromised.  An entitiy's knowledge of the shared key does not uniquely 
identify the entity.  A shared key system might be used to protect the 
exchange of further credentials, but does not by itself provide 
authentication.

  Symmetric key systems do not provide authentication, but their 
confidentiality may be used to secure a process that does -- the SYBEX 
authors may have had that in mind.

David Gillett, CISSP CCNP CCSE




 
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