> designers of Streebog and Kuznyechik purposefully hid a structure in this component. This structure is very strong, very uncommon and interacts in a non-trivial way with the other main component of Streebog.
> In light of these results, we urge security professionals to avoid these algorithms.
It's like this: imagine some government released plans for super-secure safe, and for some reason, deep in those plans, there is an instruction to make an 1/4" hole in the door, at the specific exact position. There is no justification or explanation for this hole, just a mention that it must be present or the safe is not going to be certified.
So people wonder why it was placed on the plan. If there were a good reason, why not tell it? Perhaps NSA/FSB has some new method to crack safes, and this hole is needed for it? Better be careful, and avoid using that specific safe model.
