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Re: Calling the question: derived vs. explicit IV
At 3:13 PM -0400 8/1/97, Norman Shulman wrote:
>On Fri, 1 Aug 1997, Theodore Y. Ts'o wrote:
>
>> Date: Fri, 1 Aug 97 14:32:52 GMT
>> From: "William Allen Simpson" <wsimpson@greendragon.com>
>>
>> In favor of Derived:
>>
>> 2) Maintains complete backward compatibility with RFCs 1829 and 1851.
>> All shipping implementations already support the derived IV.
>>
>> Not true. It is not _complete_ backwards compatibility. RFC 1829
>> support's no IV, 32-bit IV, and 64-bit IV. The compatibility you
>> propose only works using RFC 1829-style 32-bit IV.
>>
>> In addition the handling of sequence number wrapping means that there is
>> yet another compatibility issue. This can be solved having the ESP
>> engine know something about whether the key management was manually done
>> or not. However, that's an abstraction violation, and it certainly adds
>> to the complexity of the implementation simply to have this
>> "compatibility".
>
>Using the current ESP draft in compatibility mode requires disabling the
>authentication service. When the authentication service is disabled, the draft
>requires disabling sequence number verification.
>
>Norm
True, but sequence number generation and overflow checking is always
enabled at the sender, where the difference between a zero starting value
and a random starting value is what causes some complexity.
References: