In this case, "locked" seems like the odd one out.
Secure means it's secure, guarded, etc. So a shield, a lock, something along those lines would seem appropriate.
"Locked", however, is used as a way of saying something's not editable. This might not be the right choice given this context. (as @obelia already pointed out)
It's hard to give a practical answer without first having a look at what the interface looks like, so bear with me;
- You could attempt to make the "un-editable" elements like there's no possible interaction. Try reducing the contrast between the elements background and it's content, like how you could make an input field have a light gray background with dark gray text.
- You could attempt to make the elements with interaction methods seem more interactive. Buttons, input field borders, high contrast, etc.
This approach (rather than two different icons) also allows users a quicker overview. When attempting to see if something is "secure", rather than attempting to distinguish icons, they'll either look for icons, or for no icons. If they'd be looking for editable fields, they'd look for the interaction pattern, or the disabled pattern.
Here's a quick mockup of some combination of icons and active/disabled states. Ignore the design, tell me if you could immediately tell me which ones were secure, and which ones were disabled. Or rather, tell me what the icons and the different row styles convey.