The answer to the first part of you question ("data is not visible or tampered") is to encrypt the data. You may use file level or disk level encryption.
The answer to the second part of your question ("In case the owner forgot the password option of resetting the password should be given to him/her") is a bit trickier because it depends on the key management approach you prefer to employ; since there are many approaches, you'll have to choose one depending on your needs.
However, resetting an encryption key* is not as straight forward as resetting system access credentials (e.g. the password of your email account). This is because the key is used to encrypt the data that it protects; if you forget it then there shouldn't be a way to decrypt the data (as stated by Kerckhoff's principle). So, in order to reset the password as you mean it, you'd have to be able to re-encrypt the data with the new key - which cannot be done, since you cannot decrypt them in the first place (chicken-and-egg problem).
There are some solutions that address this problem, the first two that I can think of is to use a local password manager (not equivalent to password resetting, though) or a key escrow mechanism.
*I use the terms key and password interchangeably for simplicity, since in its most basic form a password either is the key or is used to derive the encryption key.