Problem
Question I:
You have two puzzles with parameters as follows:
Puzzle A: One sub-puzzles. k = 7.
Puzzle B: Four sub-puzzles. k = 5.
You should provide, for both cases other than part (b), the following:
1. The distribution of the number of cases that require each number of hashes.
2. Explain the method you used to obtain your distributions. Don't go into too many details or show working, it's more "I wrote a C++ program to ... and then using ... I ...".
3. A graph of the distribution of the data above.
4. The average number of hashes needed.
5. The standard deviation for the distribution of the number of hashes needed.
You should assume that if there are N possible solutions you check the Nth by hashing even if all others have failed and there has to be a solution.
Question II:
Consider that the incidence of viral attachments in email the messages in 1 in 259. Your malware checker will correctly identify a message as viral 98% of the time. Your malware checker will correctly identify a message as non-viral 98% of the time. Your malware checker has just ?agged a message as being malware.
What is the probability that the message is actually okay?