josephdrogers23/passwordgenerator

Example of a submission for a class at the University of Pittsburgh. Please refer to explanation.txt for instructions and a thorough explanation.

CS/COE 1501 Assignment 1

Posted: Sept. 18, 2015

##Goal: To demonstrate knowledge of both exhaustive search of a problem space and lookup search through the implementation of a password checker.

##Background: Let's assume that you work for a company that requires employee passwords to be 5 characters, 1-3 of which must be letters (lowercase "a"-"z", no capitals), 1-2 of which must be numbers, and 1-2 of which must be symbols (specifically "!", "@", "$", "%", "&", or "*"). You have been tasked with creating a program to check that employee passwords are "good" passwords within this space. A password is considered to be good if it does not contain any of the 500 most used English words (words from dictionary.txt), or any of these words with one or more numbers substituted for letters (i.e., "7" for "t", "4" for "a", "0" for "o", "3" for "e", "1" for "i", "1" for "l", or "5" for "s"). Your program will have two parts. First, it will enumerate all good passwords, second it will check if enetered passwords are good. If the entered password is not good, your program will recommend 10 alternative good passwords that share the longest possible prefix with the entered password.

##Specifications:

• You must implement a De La Briandais (DLB) trie data structure (as described in lecture) to use throughout your project.
• Your main program should be called from the command line one of two ways, either without any command line arguments (e.g., "java pw_check"), or with a single command line argument "-g" (e.g., "java pw_check -g").
• When called with the "-g" argument, your program should generate the list of good passwords and terminate.
  • You are provided a list of dictionary words to check in dictionary.txt. Use this file to populate a DLB trie with strings that cannot be contained within user passwords.
    • You must also write the full list of words you add to this DLB trie to a text file called "my_dictionary.txt" when your program is run with the "-g" option.
  • Use exhaustive search and pruning rules to find all good passwords. Be sure to carefully choose your pruning rules! Your search needs to be as efficient as you can make it.
    • You must write the list of good words out to the text file "good_passwords.txt".
• When called without any command line arguments, your program should prompt the user to enter passwords until they wish to stop.
  • You should use a DLB trie again to search through the good passwords.
  • For each entered password, there are two options: it is either a good password, or it is not.
    • If it is a good password, congratulate the user for their wise choice.
    • If it is not a good password, find 10 good passwords that share the longest prefix with the entered password and present them to the user as alternatives.

Due: 11:59 PM Oct. 2, 2015

##Submission Guidelines:

• DO NOT add "my_dictionary.txt" or "good_passwords.txt" to your git repository. These files must be generated by calling your program with the "-g" command line option.
• DO NOT SUBMIT any IDE package files.
• You must name your main program file pw_check.java.
• You must be able to compile your program by running "javac pw_check.java".
• You must be able to run your game by running "java pw_check [ -g ]".
• You must fill out info_sheet.txt.
• Be sure to remember to push the latest copy of your code back to your GitHub repository before the the assignment is due. At 12:00 AM Oct. 2, the repositories will automatically be copied for grading. Whatever is present in your GitHub repository at that time will be considered your submission for this assignment.

##Additional Notes:

• Generating the list of good passwords may take several minutes. Be sure to give yourself plenty of time to debug your program with this in mind.
• The list of good passwords will be rather large, be sure to account for this in how you store it.
• To increase the efficiency of your search for good passwords, be sure not to perform unnecessary dictionary checks. If you can determine that the string you are checking is not a prefix to a dictionary word, then you will not need to check further strings built off of it.
  • Also keep in mind that good passwords cannot contain dictionary words anywhere, e.g., "!5andu" is a bad password becuase it contains the word "and".
• You only need to keep in mind the number/letter replacements listed above when looking for dictionary words: "7" for "t", "4" for "a", "0" for "o", "3" for "e", "1" for "i", "1" for "l", and "5" for "s".
• Your DLB implementation must be all your own code, you cannot build the trie around Java builtin data structures such as the ArrayList or LinkedList classes.