I do not understand DigestSignInit

[Steffen Nurpmeso]

Hello.

Has anyone knowledge on how i can automatically determine whether
i need to call

  EVP_DigestSignInit(mdcp, NIL, mdp, NIL, pkeyp)

or

  EVP_DigestSignInit(mdcp, NIL, NIL, NIL, pkeyp)

That is, a way to determine whether a EVP_PKEY is "configurable
regarding the used message-digest", or whether it has a built-in
approach of digest-signing?

Any hint to overcome

  !EVP_DigestSignInit(mdcp, NIL, mdp, NIL, pkeyp) &&
    !EVP_DigestSignInit(mdcp, NIL, NIL, NIL, pkeyp)

would be very much appreciated, especially since i cannot truly
such useful non-textual info out of the error of the first (e,
GET_LIB,GET_REASON,..):

  ERROR 478150778 57 122 error:1C80007A:Provider routines::invalid digest

A nice weekend i wish everyone,
Ciao,

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)