The white paper WP_HPDM 4.7_Security_Mechanism.pdf describes more about the security thing we used in HPDM. You can easily get that from HPDM Console -> Help -> White paper
The communication between DM Components - like command task are through TLS 1.2 connection created with Open SSL.
The crypto algorithms in SSL/TLS use an RSA-created key pair of length 512 or 1024 and an X.509-created certificate. The symmetric cipher is AES (AES256-SHA).
There is no option to chagne the default cipher suite or hash as of now. But I agree that we should enhance this in the future. I would suggest you submit a request to region so that the DM team will put this as higer priority.
Please make sure the certs are included in the Certificate TRUST LIST. The whilte paper _ HPDM_Embedded_HTTPS_ServerDeployment_Guide should have included this part. You can get this in the 4.7 SP3 folder from white paper link above.