Length of public exponent in OpenPGP card specification

Werner Koch wk at gnupg.org
Sun Sep 27 13:06:37 CEST 2009

On Sun, 27 Sep 2009 00:50, klaus at flittner.org said:

> in the specification[1] the algorithm attributes contain a field for
> the length of the public exponent. The available implementation of the
> card[2] has a fixed value of 32 bits, but key import accepts a value of
> 65537 (17 bits) and key generation also produces only keys with e of
> 65537. What is the use of this field then?

It is the size of the variable describing the length of the exponent.
For example you need 17 bits to express 65537, thus it first easily into
32 bits.



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