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Type of assignment: This assignment is individual.
Points: The maximum number of points for this assignment is 49, which will be prorated accordingly after all assignments are posted. Weight of each problem is in parenthesis.
Format: Assignment submissions are accepted in the following formats only: HTML (extension .html), PDF (.pdf), ASCII text (.txt). Assignments submitted in any other format will be discarded. All text in the assignment submissions must be typed and figures plotted to be easy to read and understand. Spelling, grammar, and other language errors will result in fewer points credited to the corresponding problem solutions.
Problems
- (2 points) Submit MD5 hash value of your student number.
- (2) Download and decrypt this file, which was encrypted using AES and key "EECE 512".
- (20) Decrypt the ciphertext corresponding to your student ID from the file you decrypted in the previous problem. Determine the cipher used to encrypt the data, along with the encryption key. Submit
1) the name of the cipher,
2) the key, and
3) a description of the steps you took for recovering the key.
Attention: You cannot use any specialized tools or programs, unless you developed them yourself, for solving this problem. You can use generic tools, e.g., spreadsheet program.
- (10) You are to submit a short segment of text and a hash that is derived from a combination of the quote and your
student ID.
The quote should be at least 50 characters long, and consist only of words in the English language that can be found by querying www.dictionary.com.
The hash will be an 8 digit number computed as follows:
1. Use your 8 digit student ID to start, as the initial hash.
2. Convert your text into numbers 1 to 26, corresponding to the letters A-Z (A == 1, B == 2, ... , Z == 26).
3. Ignore all non-alphabetic characters, including spaces, and treat upper
and lower case letters as having the same value.
4. Total the converted text into 8 separate sums. Each sum corresponds to
one digit of the 8 digit hash.
5. The 8 sums will be calculated by taking the value of every 8th character
and adding it to the initial hash value (your student ID). The first sum
will be the first digit of your student ID + the value of every 8th
character of your text, starting with the first character. The second sum
will be the second digit of your student ID + the value of every 8th
character of your text, starting with the 2nd character, and so on.
6. Starting from the right to the left, modify each sum in the following way. For
each sum, looking at its closest neighbor on the right (ignore the rightmost sum
which has no right neighbor). Take the highest digit of this neighbor as a
separate number, and add it to the sum in the problem.
For example, for a sum 19, if its nearest neighbor on the right is 34, then take 3 and add it to 19,
which modifies the sum 19 to be 22.
7. Reduce the 8 sums to a single digit by performing a modulo 10 on each
sum, the resulting 8 digits will be your hash.
Example:
student id: 12345678
text: "Hello world!"
| |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
| student ID |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
| phrase |
7 (H) |
4 (E) |
11 (L) |
11 (L) |
14 (O) |
22 (W) |
14 (O) |
17 (R) |
| phrase cont-ed |
11 (L) |
3 (D) |
|
|
|
|
|
|
| total |
19 |
9 |
14 |
15 |
19 |
28 |
21 |
25 |
| modified total |
19+1=20 |
9+1=10 |
14+1=15 |
15+2=17 |
19+3=22 |
28+2=30 |
21+2=23 |
25 |
| modified total mod 10 |
0 |
0 |
5 |
7 |
2 |
0 |
3 |
5 |
Hash = 00572035
- (15) Collision Problem. Find a collision with the hash you computed from the previous problem #4.
Using the same student number as the base of the hash, find different text that will generate the same hash with your student number. The text should use only words in the English language (i.e., words available at www.dictionary.com). As a solution, provide the text, which should be different at least by one letter from the one in the previous problem.
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