[openpgp] Re: Using OpenPGP card hardware security devices w ith modern key packets

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Heiko Sch=E4fer <[email protected]> writes:

> Your proposed scheme for example is entirely hostile to casual human
> inspection of the hint field on the card, and also resists local key
> lookup using a fingerprint substring straight from the card.

Neither humans nor software should be mapping (parts of) the fingerprint
to OpenPGP card "hint" field, should they?  So if that is harder, it may
be considered a feature.

Using a hash like SHA2-256, even if truncated to 20 octets, make
accidental collisions unlikely.  An attacker needs to find a 20 octet
SHA2-256 pre-image to trigger a non-accidental collision, although the
exact threat vector is unclear to me.

I believe most software has already been changed (or should be changed)
to scan all keys on a card and see if they match whatever keys the
software wants.  The hint field should not be relied on except for
display purposes (and maybe not even that), if I understand correctly.

/Simon

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