How to generate the Siemens' DICOM "hash code value" field?

I’m trying to figure out how to generate a specific DICOM field called “Hash Code Value”, stored in a private tag called (0x0029, 0x0069) (for DICOM SEG that are segmentation made with SyngoVIA), specified in syngo via’s dicom conformance statement.

This field looks like the following b"irx7etoed3dSUPCpTgkkTguJx33D6n3qzumjKdc0N1Rtb3aLhxNU/xfh0U2y0XWISEmkCM3nt0CMcOWwQ/C5bw=="
That is a base64-encoding of a 512-bits signature, possibly a SHA512 result.

As a matter of fact, it looks like it only depends on SOPInstanceUID of the volume on which the DICOM SEG was made. in particular, the previously displayed signature was made on a series of only 2 SOPInstances of respective UID of “1” and “2”, but no matter what binary i feed to sha512, I don’t get the corresponding signature. (I tried the concatenation of both, encoding in utf-8, or inserting some separator, but nothing seems to work)

Do you know about these Siemens’ “signature” and how to generate them?