> Why do people insist on using the term zero knowledge for simple semantically secure encryption?
Note that in the domain of privacy-enhancing technologies the term "zero-knowledge" does not refer to "semantically secure encryption". Instead it is used to mean that a service provider does not have access to user data, and that this claim can be proven cryptographically. The use of the term zero-knowledge to promote privacy-respecting services dates back to at least 1997 with the founding of the Canadian company Zero-Knowledge Systems [1], which provided anonymous communication services [2].
I don't dispute that fact. But there is precedent for the use of the term in privacy-respecting services, so we shouldn't be surprised when we encounter it. After ZKS shut down, the term continued to be used by hosting and communications services to explain their value proposition in a simple way.
Having said that, I agree with the point that nowadays this usage may be unhelpful in promoting privacy-respecting services because zero-knowledge proofs have come a long way and there are now services like Zerocash that actually make use of them. So using the term to promote a different privacy-respecting feature may be confusing or misleading.
I wish they would pick a clearer term that's not already in use, like (as I think they mean in this case) "provider-obscured". Heck, even "homomorphic" would be better, as that signifies "does stuff you want with your data, without knowing the content of said data".
Then that is a pretty poor precedent, however I've not seen people (who actually understand cryptography or security) reference "zero knowledge" as the fact that the provider can't access your data.
Alternatively, based on my assumption that English is only a second language for the authors[1] I also think it might just be a cultural/language issue. Being a non-native english speaker myself, I frequently find myself differing in word usages with the native speakers. And there is probably no formalized naming convention (like scientific names in biology), it's what's all in people's heads. What Fowler said about naming being hard is probably very true [2].
Note that in the domain of privacy-enhancing technologies the term "zero-knowledge" does not refer to "semantically secure encryption". Instead it is used to mean that a service provider does not have access to user data, and that this claim can be proven cryptographically. The use of the term zero-knowledge to promote privacy-respecting services dates back to at least 1997 with the founding of the Canadian company Zero-Knowledge Systems [1], which provided anonymous communication services [2].
[1] https://en.wikipedia.org/wiki/Zero_Knowledge_Systems [2] http://edition.cnn.com/TECH/computing/9902/11/browsanon.idg/