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Re: Manual keying and replay prevention
Norm,
I inserted the cited note re manually positioned keys was because I
assumed that these keys would not be changed frequently (to assume
otherwise would facilitate a management vulnerability) and because I
assumed that saving state for the anti-replay sequence number would be
problematic (across crashes, etc.). Under these assumptions, counter
cycling becomes a problem. It does not seem to be realistic to assume that
a manually positioned key would be changed in a timely fashion as the
counter neared 2**32-1. These are conservative assumptions, but this is a
security protocol, so such assumptions are not necessarily out of line.
Later e-mail from others attempts to clarify the use of the phrase
"manual keying," but I based this text on the prevous IPsec RFCs, where the
intent (Ran can confirm this) was to refer to symmetric keys.
Steve
References: