Are there any known vulnerabilities in the GOST block cipher (GOST 28147-89)? Spcifically, I'm thinking about i.e. "master keys" which intentionally exist and are used i.e. by the Russian government.
I understand that although there are attacks against the algorithm itself, it is not broken. Is this a correct assumption?
However, it would not help the algorithm in terms of security if there were for example master keys which would allow the Russian government (or whomever, I'm using the Russian government as an example, since GOST is a Russian algorithm, for all I know) to access files encrypted with this algorithm.
If GOST would be used in a chain of several algorithms, i.e. AES-TWOFISH-GOST, would there be a risk of weakening AES and/or TWOFISH assuming GOST had known vulnerabilities like the one described earlier?
Also, is GOST used anywhere outside Russia or is it a strictly Russian algorithm?
Thank you very much.