20160830143639_create_students.rb

create_table :students do |t|
  t.string :first_name
  t.string :last_name
  t.string :citizenship
  t.string :rodne_cislo
  t.string :group
  t.date :date_of_birth
  t.string :studies_state
  t.string :primary_specialty
  t.string :secondary_specialty
  t.string :foreign_language
  ...
end

20160907131036_devise_create_users.rb

create_table :users do |t|
  ## Database authenticatable
  t.string :email,              null: false, default: ""
  t.string :encrypted_password, null: false, default: ""

  ## Recoverable
  t.string   :reset_password_token
  t.datetime :reset_password_sent_at

  ## Rememberable
  t.datetime :remember_created_at

  ## Trackable
  t.integer  :sign_in_count, default: 0, null: false
  t.datetime :current_sign_in_at
  t.datetime :last_sign_in_at
  t.inet     :current_sign_in_ip
  t.inet     :last_sign_in_ip

  t.timestamps null: false
end

20160910100918_create_imports.rb

create_table :imports do |t|
  t.integer :creator_id
  t.string :source
  t.string :status

  t.timestamps
end

20160910101202_create_exports.rb

create_table :exports do |t|
  t.integer :creator_id
  t.string :result

  t.timestamps
end

edit.html.erb

<% title @user.email %>

<%= page_header 'Editovat uživatele' %>

<div class="panel panel-defult">
  <div class="panel-body">
    <%= form_for @user do |f| %>
      <div class="form-group">
        <%= label_tag 'Email' %>
        <%= f.email_field :email, class: 'form-control' %>
      </div>

      <div class="form-group">
        <%= label_tag 'Heslo' %>
        <%= f.password_field :password, class: 'form-control' %>
      </div>

      <div class="form-group">
        <%= label_tag 'Potvrzení hesla' %>
        <%= f.password_field :password_confirmation, class: 'form-control' %>
      </div>

      <button type="submit" class="btn btn-primary">Uložit</button>
    <% end %>
  </div>
</div>

encryptable.rb

module Encryptable
  def encrypt_columns(*columns)
    columns.each do |column|
      if self.column_names.include?(column.to_s)
        define_method "#{column}=" do |value|
          self[column] = self.class.crypt.encrypt_and_sign(value)
        end

        define_method "#{column}" do
          self.class.crypt.decrypt_and_verify(self[column])
        end
      end
    end
  end

  def crypt
    salt = ENV['crypt_salt']
    key = ActiveSupport::KeyGenerator.new('password').generate_key(salt)

    @crypt ||= ActiveSupport::MessageEncryptor.new(key)
  end
end

student.rb

class Student < ApplicationRecord
  encrypt_columns :first_name, :last_name, :rodne_cislo
  
  ...
end

users_controller.rb

class UsersController < ApplicationController
  before_action :authenticate_user!, only: [:index]
  before_action :set_user, except: [:index]

  def index
    @users = User.all
  end

  def edit
  end

  def update
    @user.update_attributes(user_params)
    redirect_to users_path
  end

  def destroy
    @user.destroy
    redirect_to users_path
  end

private

  def set_user
    @user = User.find(params[:id])
  end

  def user_params
    params.require(:user).permit(:email, :password, :password_confirmation)
  end
end