Deciphering a .p7f file

[Keine Eile]

Hi list members,

I have a .p7f in hands, which seems to be a DER encoded PKCS7 structure in some way, I can use 'openssl pkcs' to transform it in a PEM form, I also can pull a bunch of certificates out of it. But I know, there is some encrypted pay load in this file, which I can not decipher. What I have tried with openssl's rsautl and smime does not seem to work for me.

May be someone of you can push me in the right direction, thanks!