Enveloped-data content type of the cryptographic message syntax defined in RFC 2630

Hi there,

I need to encrypt some content in an Enveloped-data content type of
the cryptographic message syntax defined in RFC 2630.

I thought first using xyssl / polarssl, but because of lack of
knowledge in this field and the lack of a stronger xyssl community I
am not making any progress.
Could someone please let me know if there is another library that
would be a better fit for me:
* must be open source,
* portable
* written in C/C++
* available under BSD style license

Thanks,
Mathieu
.