How we can implement the encryption for different clients in one app of same instance?
Discussion posts and replies are publicly visible
I think you should provide a few more details.
codeblog.jonskeet.uk/.../
If we have 10 clients, how can we manage them, whether they are on different Appian instances or the same Appian instance? In the case that we manage the data on the same instance, how can we ensure its security?
You can ensure the security by using Record Level Security.
Why does the data need to be encrypted with separate keys?
This is such a broad and potential difficult to answer topic! We need a lot more details!