Yeah but you need to get one to begin with tbh. Kilo's especially later mods (Pr.636, 636.3) and newer Russian Subs (Yasen/Yasen-M, Borei-A/Borei-B) are still not identifiable completely because, well, your USN still hasn't managed to get a Signature of them properly, something that even Supercomputers at AUTEC of the NUWC working under the direction of USN's NAVSEA can't recreate or simulate even if they fed data from grainy photos of those props. Simulations also are still just an approximation of the real thing, not the real thing itself. So while you can keep everything under lock and key, you still are missing signatures of Subs that you're more likely to encounter in the future.
Since we are discussing nuclear submarines and stealth, an idea occurred.
Now almost everybody knows that Luneberg lenses are used to increase the radar reflectivity of aircraft(for purposes of masking and misleading enemies about the actual stealth parameters of the aircraft).
Now suppose an nuclear submarine fields an marine equivalent of the Luneberg lens which purposely increases the acoustic and magnetic signatures of the submarine by a small percentage, say about 10% to 25%. The increase should be a small percentage only(marginal) as we don't want the submarine to appear like an gigantic piece of iron on enemy sonar screens.
Also the Luneberg lens equivalent attachment should be capable of being jettisoned when required.
The submarine's acoustic and magnetic signatures even with the Luneberg lens like attachments should be near the capability of enemy submarines. We don't want to create an inferior submarine.
Now imagine that an actual war breaks out. The role of SSN's and SSBN's will be crucial to determine and change the course of the war.
Now the enemy may have collected the acoustic and magnetic signatures of the submarine beforehand by shadowing and signal intelligence operations. These signatures would be stored in the appropriate threat libraries.
But imagine that when the real war starts the command is given to the submarine to jettison and throw away the Luneberg lens equivalent equipment. So suddenly the submarine will become more stealthier and harder to detect. Its present acoustic and magnetic signatures will not match the recorded performance parameters as stored on enemy databases.
The advantage will be short lived but could possibly influence the outcome of the war.
Now whether something like this is technically feasible is to be seen.