Re: [pki-tc] Extranet S/MIME?

[Arshad Noor <arshad.noor@strongauth.com>]

Catherine,

Encryption in S/MIME works counter-intuitively to what one expects -
the decryption of encrypted S/MIME messages does not require the
sender to have a digital certificate at all (he/she does need to
have the RECIPIENT's certificate though, to encrypt the message in
the first place).  The recipient need only have the private key to
their encryption certificate to decrypt the S/MIME contents.

If your goal is only encrypted S/MIME, then you do need to setup a
repository (typically, an LDAP directory) where the encryption cert
of the recipient is available to senders.  If setting up such a
repository is not feasible, an alternate way to ensure that senders
have the recipients' encryption certificate is to have the recipients
send a digitally signed e-mail to all senders.  This automatically
sends the the signers' digital certificates in the S/MIME object.
Compliant S/MIME tools - such as Netscape's Messenger, Outlook
Express, (haven't tested Thunderbird yet - but will probably work)
will automatically import the senders' digital certificates into the
local address book.

The next time the sender wants to send the recipient an encrypted
message, the recipients' encryption cert will already be available
to them locally to perform the encryption, thus obviating the need
to access a repository for the encryption cert.

Hope that helps.

Arshad Noor
StrongAuth, Inc.

licather@wellsfargo.com wrote:
> Hi All,
> 
>  
> 
> I'm seeking expert opinions and recommendations how to support S/MIME 
> communications in an extranet. Specially, decrypting an encrypted email 
> from another company, i.e., the recipient needs to get hold of the 
> certificate of the email author’s. Does that mean, there needs to be an 
> extranet directory service to facilitate obtaining certificates? If not, 
> what service needs to be setup to facilitate that?    
> 
>  
> 
> Thank you in advance,
> 
> Catherine Li
> 
> CAST PKI Development
> 
> Wells Fargo Services
> 
> Office:   415.243.6228
> 
> Fax:      415.975.6780
> 
> MAC:    A0186-056
> 
> Email:   licather@wellsfargo.com
> 
>  
> 
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