發送短信 : Formal analysis and systematic construction of two-factor authentication scheme

   _____   _    _    ______      ___      _  __  
  / ___// | || | || |      \\   / _ \\   | |/ // 
  \___ \\ | || | || |  --  //  | / \ ||  | ' //  
  /    // | \\_/ || |  --  \\  | \_/ ||  | . \\  
 /____//   \____//  |______//   \___//   |_|\_\\ 
`-----`     `---`   `------`    `---`    `-` --`