Smart cards

Werner Koch wk at
Thu Dec 13 08:13:58 CET 2018

On Tue, 11 Dec 2018 19:27, arthur at said:
> using openkeychain with a yubikey nfc is totally solid, and convenient.
> I've been using them for years. they also plug into the bottom of the
> phones which some people prefer.

You should keep in mind that you can eavesdrop on NFC communication
within several meters.  Right, it is required that the card is niot more
than about 10cm away from the reader but that is only to convey the
power to the card, the HF is readable from several meters as soon as the
card is powered up.

If you care about side channel attacks, NFC communication is a bad idea
because the decrypted session key can easily be picked up.  To avoid
this, /secure communication/ needs to be used but that is cumbersome
because this requires a shared secret between host and card.  But well,
smartphones are not a safe device anyway.



Die Gedanken sind frei.  Ausnahmen regelt ein Bundesgesetz.
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