HTW Berlin Fachbereich 4 Internationaler Studiengang Internationale Medieninformatik (Bachelor) Aktuelle Themen: Cryptography Winter Term 2024/25

Lab 10: Dictionary Attack

1. Find an online, easy to read dictionary. You can either use one offered as a web service (Hint: Google) or download any of the fine dictionaries that abound. Mac users have a special bonus here - there is a dictionary installed on your machine. Where is it?
2. Use your solution to the Symmetric Cryptography exercise to generate secret messages that are encrypted with a word from the dictionary as the key (maybe choose a random one?) using Blowfish and ECB. Post these in the Secret Messages forums area! Encrypt a second message that uses a slightly better key - a word chosen from the dictionary with one digit on the end, or the beginning, or 1 instead of i, or 0 instead of o, etc. Each group posts at least two messages, more if you are in the holiday spirit that are even meaner!
3. Write a program to mount a dictionary attack on the messages! How long does your program need to break the simple ones? What is its complexity?
4. (For the bored) Improve your program to crack the second message with one digit included in the key!
5. (For really bored) Improve your program so that you can mount a dictionary attack with multiple numbers added, special characters, common first names, common dog names, "letmein", etc.