It's interesting how Rigol did the locking of those extra features. The unlock key for a feature set for your scope has to be signed by a Rigol private key using an elliptic curve signature system.

But they are only using a 56 bit private key. That was quickly brute forced, and key generators proliferated.

They used a good library for the cryptography stuff, and except for the short key seem to have used it well and knew what they were doing. This suggests that the choice of a weak key was deliberate.

Each family of scopes has its own private key. As few families came out with new private keys, Rigol continued to use 56 bits. When major firmware upgrades came out in existing families, where they could have easily changed to a longer private key, they kept the same 56 bit that was now widely circulated on the net.

It seems pretty clear that they are not interested in stopping people from free unlocking.