What makes you think that a password is encrypted?
It shouldn't be: that's insecure, nearly as bad as storing it in plain text.
And System.Text.Encoding has nothing whatsoever to do with encryption - it's a translation, is all.
Passwords should be hashed, not encrypted - specifically so thay cannot be "reversed" back to the original input.
See here:
Password Storage: How to do it.[
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