Cracking Codes with Python

10ENCRYPTING AND DECRYPTING FILES

“Why do security police grab people and torture them? To get their information. And hard disks put up no resistance to torture. You need to give the hard disk a way to resist. That’s cryptography.”—Patrick Ball, Human Rights Data Analysis Group

In previous chapters, our programs have only worked on small messages that we type directly into the source code as string values. The cipher program we’ll make in this chapter will allow you to encrypt and decrypt entire files, which can be millions of characters in size.

TOPICS COVERED IN THIS CHAPTER

• The open() function

• Reading and writing files

• The write(), close() ...