Quote: file content should be encrypt at client end ... and should be decrypt at service end
What you are describing is precisely what HTTPS does:
HTTPS - Wikipedia
All requests and responses are encrypted over the wire, and can only be decrypted by a computer with access to the private key.
Implementing your own encryption on top of this would not increase the security of your application in any way.
(If you were talking about end-to-end encryption, where the server cannot decrypt the uploaded file, that would be a different story.)