I read an article in which I saw
Sandra cryptography benchmark
My question is shouldn't it be
Sandra cryptographic Benchmark
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Both are fine.
Noun-noun compounds are very common, especially in technical fields.
In some cases, there could be a difference in meaning. "A cryptographic benchmark" could also mean "a benchmark (for some other field) which is cryptographic in nature", whereas "a cryptography benchmark" unambiguously means "a benchmark relating to cryptography". I don't think this ambiguity is likely in this case, but it could be in other cases.