利り用よう者しゃの認にん証しょう

• 認にん証しょう

  認証 is the general term for authentication or certification; 利用者の認証 specifies that it is for users.

• ログイン

  ログイン refers to the act of logging in, which often includes authentication, but 利用者の認証 focuses on the verification process itself.

Compound of 利用者 (user) + の (possessive particle) + 認証 (authentication). A straightforward technical term.