Create key's over 4096 bit ????

Johan Wevers johanw at
Wed Dec 21 16:36:28 CET 2005

Holger Schuettel wrote:

>I've any questions. How can i generate a keypair with size  more than
>4096 bits? I've a RSA key from my friend in my keyring with 16384 bits.
>How is that possible?

It's probably created with one of the many hacked versions of pgp 2.x that
are around. The 2048 bits 2.x enforced was an arbitrary cutoff - the code
could be used for 16k keys max.

>I've to try it with gnupg to generate a key over
>4096 bits and thats not possible. Can you help me ?

I'm sure it's possible to hack the gpg sourcecode to do it. I found in
g10/keygen.c the lines:

static unsigned
ask_keysize( int algo )
  unsigned nbits,min,def=2048,max=4096;

If you change the max= into the size you want, I think it would work.
I don't know how large RSA keys the gpg code can really handle, so I
would do a bit more checking before you adapt your gpg version.

>(german answer preferred)

Sorry, my German writing is far worse than my English.

ir. J.C.A. Wevers         //  Physics and science fiction site:
johanw at   //
PGP/GPG public keys at

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