Purpose: This assignment provides experience with encryption.
1) Get a copy of the instructors do_crpyt.c program.
Compile it and run it. Make sure you can explain what the program prints. (Don’t turn anything in for this part.)
2) Redo homework 2 (copy.c) (yet again).
a) As you make the copy, encrypt (or decrypt) each block before you write it. The key may be embedded inthe code (like my example).
b) Add a fourth commandline parameter to your copy.c. If the argv[3][0] is ’e’ encrypt while doing the copy. Otherwise decrypt.
Hint: place an if statement before you start the copy, set a variable to either DES_ENCRYPT or DES_DECRYPT. Use the variable in your copy.
Example:
a.out encrypt.c crypted_file e Produces an encrypted version of encrypt.c
a.out crypted_file encrypted_copy.txt d
Produces an encrypted version of crypted_file (which should be identical to the original file).
File: encrypt.c is a copy of what I used in lecture. It should compile and run.
