Password form registrasi codeigniter

bagaiamana caranya supaya form registrasi pada kolom password bisa menjadi sha1?

    public function registration()
    {
        //  Section1 //
        $this->form_validation->set_rules('nama_lengkap1', 'Nama_Lengkap', 'required|trim');
        $this->form_validation->set_rules('email', 'Email', 'required|trim|valid_email|is_unique[user.email]', [
            'is_unique' => 'This email has alrady registered!'
        ]);
        $this->form_validation->set_rules(
            'password1',
            'Password',
            'required|trim|min_length[5] |matches[password2]',
            ['matches' => 'password dont match!', 'min_length' => 'Password too short!']
        );
        $this->form_validation->set_rules('password2', 'Password', 'required|trim|matches[password1]');
           ];
            $this->db->insert('user', $data);
            $this->session->set_flashdata('message', '<div class="alert alert-success" role="alert">
            Selamat! Akun anda telah terdaftar. Silahkan masuk!  </div>');
            redirect('auth/login');
        }
    }

        if ($this->form_validation->run() == false) {


            $this->load->view('templates/auth_header');
            $this->load->view('auth/registration');
            $this->load->view('templates/auth_footer');
        } else {
            $data = [
                'nama_lengkap' => htmlspecialchars($this->input->post('nama_lengkap1', true)),
                'email' => htmlspecialchars($this->input->post('email', true)),
                'password' => password_hash($this->input->post('password1'), PASSWORD_DEFAULT),
                'photo' => 'default.jpg',
                'role_id' => 2,
                'is_acvtive' => 1,
                'date_created' => time()
            ];
            $this->db->insert('user', $data);
            $this->session->set_flashdata('message', '<div class="alert alert-success" role="alert">
            Selamat! Akun anda telah terdaftar. Silahkan masuk!  </div>');
            redirect('auth/login');
        }
    }