Defensive Design

Defensive Design

1. helps ensure programs function properly

   • when programs are functioning correctly they should never break and never produce errors. in practice this is difficult to achieve
   • make sure the inputs cant be exploited
     • input sanitation is removing unwanted characters before passing data through the program
     • input validation is checking if the data meets certain criteria before passing through the program
       • sanitation and validation are often done using whitelists and blacklists.
         • whitelists tend to be more secure, however they can take a long time to set up and can be too restrictive
           • a whitelist is a list of all data that a program should accept - any data that isnt on the whitelist should be rejected
           • authentication can help protect your programs
             • authentication can confirm the identity of a user before they are allowed to access certain pieces of data or features of the program
               • passwords are usually associated with username. when someone tries to access a protected part of the program, it should ask them for their password to check that they are who they claim to be.
         • a blacklist is a list of all the data that a program should reject - any data that isnt on the blacklist will be accepted

2. translators

   • most of the programming languages that you'll be familiar with are ;python, C++, java script are all high level languages. the source code is easy for humans to write but computers need to translate it into machine code before they run it
     • on the other hand, low-level languages are tricky for humans to read and write but are easier for computers to run. they consist of machine codes and assembly languages
   • compilers - translate all the source code at the same time. only needed once to create an executable file. returns a list of errors for the computer to run after compiling is complete . once compiled the program runs quickly but compiling can take a long time
     • interpreter - translate and runs the source code one instruction at a time, but doesn't create and executable file.