The point is that you can’t have enough information to decrypt it and (at least in the United States) it’s against the law to divulge it or to reverse engineer it.
On SACDs the keys are encoded in the widths of the pits on the SACDs TOC. (Except for varying pit widths the DSD layers of an SACDs are just a DVD layer.) I seem to remember that it was some sort of public key encryption, but don’t quote me.
FWIW I don’t know exactly how the data will be encrypted coming from the new transport, but presumably PS Audio will tell me at some point so I can make an FPGA that can understand it
 I guess I could add that you could look up the datasheets for an HDMI support chip that handles DSD and you’d get an idea about how the HDMI hardware supports DSD encryption.
Tho I mentioned HDMI and PS Audio’s I2S link is over an HDMI cable and HDMI connectors it’s not HDMI and PS Audio will be inventing their own encryption to keep the raw bits from being exposed in the wild.