How to import external RSA keys

Moritz Schulte mo at
Sat Jun 11 17:15:06 CEST 2005

On Wed, Jun 08, 2005 at 12:54:32PM +0200, Carolin Latze wrote:

> Has anybody an idea how to import these keys into a program written
> with the gcrypt.h?

I cannot give advice on the procedure of extracting the key from that
specific card, I can give general advice, though: as you probably
know, an RSA key consists of a few numbers (the so called `key
material').  What you have to do is:

  * extract these numbers
  * figure out the format of the numbers
  * convert the numbers into a format supported by Libgcrypt
  * make sure that the semantics regarding the numbers p, q, u match
    those of Libgcrypt (u might need to be recomputed),
  * convert the numbers to Libgcrypt MPI objects
  * construct a complete key from the raw key material using either
    the sexp/pk interface or the ac interface.

Hope this help a bit,

Moritz Schulte

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