NULL_ESP; why at all does it exist?

[venkat <venkat@dexceldesigns.com>]

Hi Everbody,

Could you answer these questions

1. During ESP packet generation, can the encryption be done with DES_CBC or 
3DES_CBC and then provide authentication with NULL_ESP.

2. Is it required that we have to provide authentication with HMAC-MD5 or 
HMAC-SHA. i.e. ESP_AUTH part

3. Can NULL_ESP be used for providing authenticatoin at all, because I read 
somewhere that NULL_ESP can be used for this purpose.

4. Is NULL_ESP a void Transform, i.e. it doesn't do anything at all.

5. To provide authentication only in ESP, can we use Enc-> NULL_ESP and then
Auth-> HMAC-MD5/SHA

Awaiting replies
- Venkat

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Dexcel Electronics Designs (P) Ltd., Bangalore, India