Add masterkey as subkey to new masterkey

[Ángel]

On 2021-04-10 at 04:08 +0000, Kiara Stankovic wrote:
> Hello gnupg-users,
> 
> I want to add my existing master key as a subkey to a new master key.
> 
> I have followed the steps at 
> https://security.stackexchange.com/questions/32935/migrating-gpg-master-keys-as-subkeys-to-new-master-key
> , and I was able to slot in my subkey, as well concatenate it into
> one file as well, but while importing it (with the latest version of
> gnupg) I encountered an error - bad signature, realizing that I had
> to use an old version of gnupg - around 2005, but I did not have
> access to any such gpg binaries.
>  
> Are there any workarounds for this?
> Adding a subkey with keygrip also doesnt work, since the new subkey
> has a different keyid than the original key.
> 
> Can someone help me?
> --
> Kiara Stankovic

The solution of https://security.stackexchange.com/a/160847/ should
work fine. What do you mean with "the new subkey has a different keyid
than the original key" ? Note you need to use the keygrip, not the
keyid.

Maybe you could provide the steps you are doing along with its output?