[Cryptography] Two quick questions about IPsec AH

[Bill Frantz]

On 1/11/22 at 2:45 AM, kivinen at kivinen.iki.fi (Tero Kivinen) wrote:

>>So I rather doubt EH is used because I doubt any of the kludges were
>>implemented for anything besides ESP. And besides which, there is a null
>>cipher for testing and for environments where you want authentication but DO
>>NOT want encryption (this is very common in SCADA deployments and for
>>excellent reasons)
>
>ENCR_NULL is not only for testing, it is also in situations where you
>do not want to do encryption (for example if traffic is already
>encrypted, so there is no point of encrypting it second time), but do
>want to do integrity and authentication checking.

There are some places where secrecy may be a negative. One 
example is that anything that goes over a amateur radio link. 
Encryption for secrecy is specifically illegal in the US Federal 
Communications Commission regulations. However, encryption for 
authentication and integrity is specifically permitted, and 
useful if the link is e.g. controlling a remote station.

Remote station control is similar to SCADA uses. With SCADA, it 
may be very useful to have network monitors that can see the 
commands and responses sent to the devices without being able to 
send commands themselves. It may also be useful to have monitors 
that don't need to be running during the key exchange protocols. 
Network monitoring of non-secret data is an easy way to 
accomplish these goals.

Otherwise, the system will need separate keys for secrecy and 
for authentication/integrity, making the system more complex and 
therefore probably less secure.

Cheers - Bill

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