1. Consider the Manchester Encoding technique.
a) Explain how a text (or a message) can be encoded by the Manchester encoding technique.
b) Pick the first character of your last name in uppercase and convert it to a binary code in 8 bits. For example, James Smith takes “S” to convert into a binary. What is the binary code of your last name initial?
c) Assume the clock bits are 10101010…. In this pattern. What is the encoded bits by applying the Manchester Encoding technique?
d) How can you decode it? Explain briefly.
2. Suppose that your laptop connects an access point (AP).
a) List the steps that take place at a laptop when it needs to connect an AP.
b) RC4 algorithm is a foundation of WPA2. Explain the concept (not the algorithm itself) of RC4 briefly.
c) How a streaming key is used to encode a text in WPA2? Explain it briefly.
d) Consider the key = 1234 and the text = 7788. Apply RC4 illustrated (simplified) in class. What is the first key? Show the computation step:
HW5 A5/1 Encryption
This assignment is to practice A5/1 encryption. Refer to the feedback polynomials with the same clocking bits as the one discussed in class. Consider the following three registers to generate a key stream.
Message to send: K
R1 = [1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0]
R2 = [1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0]
R3 = [1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1]
Please note that
– the LFSR represented in a list is opposite to that explained in the class slides. It means that R1 above the first bit is on the left, and the last 19th bit is on the right end.
– the clock bits of LFSR are 9th, 11th and 11th of R1, R2 and R3.
– The tapped bits for XOR from R1: 14th, 17th, 18th and 19th bit
– The tapped bits for XOR from R2: 21st and 22nd bit
– The tapped bits for XOR from R3: 8th, 21st, 22nd and 23rd bit
4.1 What is the operation to generate the first bit of the stream key?
4.2 What is the first bit of the key?
4.3 According to the clocking bits, which registers are picked for feedback?
4.4 What are the the first bit (indexed by 0) of each register, after feedback and shifting bit at the first key generation?
4.5 What is the first bit of the key?
4.6 What is the second bit of the key generation?
HW4 rc4 streaming encryption
Review the class slides of wifi streaming crypto algorithm, rc4.
Consider the following to apply to rc4 algorithm using an array of 8 bytes (You may want to rewatch the video lecture!).
Key T: 7136
Now consider the message P to send. Let P = [ 5 5 5 3 ].
Step 1: Apply the Initialization Algorithm, discussed in class. By applying the first three iterations,
1) give the list S at each step of those three iterations.
Answer the following:
a. Show S for i=0
b. Show S for i=1
c. Show S for i=2
2) What is the first two keys?
3) What is the cipher for that first message 5?
4) What is the key to be generated for the second 5? What is its cipher?
Answer all in plaintext
a) Explain the concept of steganography.
b) Show the steps of hiding a text message into an image according to the steganography concept described above.
c) Show the steps of extracting the text message from the stegano image stepped above.
d) Apply the method discussed in class to extract a character from the following RGB code. The method that you should apply is to take the least insignificant bit of each R, G and B color.
R G B
254 125 99
255 124 98
255 125 99
255 125 99
255 125 99
HW4 Network Forensic (5pts)
Raspberry Pi is one of the most poswerful microcontrollers, on which Raspbian can run. Raspbian is one of the debian Linux distributions, and install a wifi access point (AP) and wireshark.
Wireshark is one of free and open-source packet analyzers. Using pcap (), there are tools capturing packets in GUI (Wireshark) and non-GUI (command-based TShark) running on cross-platform, released under the terms of the GNU.
1. Let your cell phone access the AP. Extract packets of your cell phone accesses and let given packets be contained in the file Packet.txt
2. Extract the IP assigned to your cell phone.
3. After that, filter wireshark packets to collect all activities of your cell phones (text, phone calls, internet through wifi).
1) screenshot of wireshark showing your cell phone IP
2) screenshot of wireshark packets about your cell phone accesses
HW3 Image Forensic (5pts)
One of the widely-used images formats used by most smartphones and digital cameras is JPEG. JPEG image format has two types of compression: JFIF and EXIF.
Consider the two photo images
1) Extract the following metadata from the photos
2) Plot the physical locations of those photos on the google map (manually or by using plotter).
3) Describe a possible (fiction) criminal story which may be used as evidence.
1) a. Time; b. Latitude; c. longitude; d. Altitude, in plaintext
2) A google map image, or your camera photo
3) Description in plaintext