Encryption does not "add", like error/noise, it translates. The signal-to-noise ratio stays the same. Another way do describe it is that error correction creat

Encryption does not "add", like error/noise, it translates. The signal-to-noise ratio stays the same. Another way do describe it is that error correction creates resistance against (effectively) some upper boundary of error/noise. It does that by essentially multiplying the signal so that (with a still constant error) it increases the effective SNR , as that is just signal divided by error. It cannot work if you have 100% noise and 0% signal (it's intuitive why, and 0 multiplied by x is still 0). A good encryption scheme however (pretty much any common one that isn't a toy) has the goal of making the signal look entirely random for anyone without the proper algorithm and secret to reverse. With an effectively 0 SNR to that observer, there is no signal to boost. Noise/error is random, if it wasn't it would be reversible and not need any error correction techniques that effectively reduce bandwidth. Encrypting, however, is not random at all, it is entirely deterministic, making it intentionally reversible.