At what level are you encrypting? CRM 2013 supports encrypted databases if you're worried about the data at rest.
In transit, you should be using SSL to encrypt the entire process, not just individual data.
you can use field-level security to not display certain fields to end users of a certain type if you're worried about that. It's even more secure than anything you could do with JS, as the data is never passed over the wire.
Is there something those don't solve?
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