Test 1

You will answer the questions with either fixed answers, short explanations or with multiple choice. The test is a closed-book test. Note there will be no lectures or labs in Week 9. The table you will be given is here.

Time for test: Wednesday, 1 November 2023 (9am-11am, JKCC)

Background

• Ciphers and Fundamentals Link.
• Symmetric Encryption/Hashing Link
• Public key. Link
• Key Exchange. Link
• Digital Certificates. Link

Test 1 (Challenges)

• Hex Code Challenge Try.
• Pigpen Try.
• Polybius Try.
• Morse Try.
• ADFGVX Try.
• Scrambled Alphabet Try. Can you beat 5 minutes?

Test 1 (Examples)

• Rail Code Try.
• Caeser. Try.
• Hex. Try.
• Binary to ASCII. Try.

Test 1 (Some principles)

• Key Enthropy here. How many bits can represent X phases? Just take the Log(X), and divide by Log (2).
• John the Ripper, Hashcat and Ophcrack: here
• Using OpenSSL to salt passwords: here

The table you will use in the test is: here and you can use a calculator.

Here are some sample tests:

• Test 1 (Fundamentals)
• Test 2 (Encryption)
• Test 3 (Cracking)

Study Questions

Try to review your knowledge by answering these questions:

• Can you convert characters from one format to another, such as in binary, hex, ASCII and Base-64 (remember: hex uses four bits at a time, and Base-64 uses six bits at a time)?
• Do you know the basic theory of converting a bit stream into Base-64 (remember 6 bits at a time and convert from table)?
• Do you understand how to use some key ciphers, including shifted alphabet, led alphabet, Vigenere, Pigpen and rail codes?
• Can you do a simple Diffie-Hellman calculation and end up with the same shared key?
• Do you understand how the number of keys relate to the security of the ciphers?
• Can you work out key enthropy, so that if you have 2,048 phases, you can calculate that this is equivalent to 11 bits [log(2048)/log(2)]?
• Would you know how long it would take to crack a code next year, if it takes 10 years now, and computing power doubles each year?
• Do you understand how public and private key encryption is used, along with the usage of digital certificates?
• Do you understand the conversion of passwords into hashed passwords, and use tools such as John The Ripper, Hashcat, Ophcrack and OpenSSL?

Possible study areas:

• Solve ASCII hexadecimal encoding.
• Solve ASCII binary encoding.
• Solve Morse encoding.
• Solve the shifted alphabet code.
• Create the Vigenere Code for a given plain text string and key.
• Able to convert bit streams to hexadecimal.
• Able to convert binary streams to Base 64.
• Solve Playfair codes.
• Solve Rail codes.
• Solve scrambled alphabet code. Some samples are here here here.
• Calculate the entropy of passwords.
• Calculate simple Diffie-Hellman.
• Determine time to crack a code, on average, given time to test key.
• Determine time to crack a code, for increasing computing power.
• Understands how public key encrypts data.
• Understands how public key is used to provide identity.
• Understands the key elements of a digital certificate.
• Understand the processing of salting a password and its usage in encryption.
• Password hash cracking/salting (LMHASH/MD5).

Tables given are ASCII table, Morse and Base 64.

What about I know from a practical point-of-view?

The two main labs you should know about are here:

• Lab 5: Crypto - Lab 5.
• Lab 6: Crypto - Lab 6.