MUA option "encrypt to self" weakness in certain situations?

[Atom 'Smasher']

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On Sun, 25 Apr 2004, Malte Gell wrote:
> This could mean that if someone (=recipient) uses a long key it may be
> rendered "useless" without intention if the sender has a short(er) key
> and uses such an "encrypt to self" option in his MUA. Is this thought
> correct?
=====================================

correct. this is the case *anytime* multiple recipients are specified, not
only the case of encrypt-to-self. if an attacker wants to know the session
key, they can attack the "weakest" public that a message is encrypted to.

as i understand it, the public key implementations does not help an
attacker compute another private key, used in the same message.

part of the security of ANY encryption scheme depends not just on how
secure/paranoid ~you~ are, but also how secure/paranoid is the person
you're communicating with. a mistake on *their* end can cause *your*
secrets to not be secret.


	...atom

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