# MACHINE LEARNING AND CRYPTOGRAPHY computer science questions 2 QUESTIONS

**Learning Goal: **I’m working on a computer science question and need an explanation and answer to help me learn.

Cryptography

1. Show, using worked out examples, that for RSA, PB(PR(M))=M

and PR(PB(M))=M, where PB, PR and M, respectively are the public

key, the private key, and the plaintext. Design the keys using prime

numbers 11 and 17.

NATURAL LANGUAGE PROCESSING

Show your work. Correct answers with no work shown will receive no points.

**Problem 1: Viterbi Decoding**

**(**a) Using the matrices given, compute by hand the Viterbi trellis (as shown in Figures 6.10 and 6.12) and backpointer matrix (as used in Figure 6.11) for the sentence “Dumbledore fed his phoenix peanuts”. **(3pts)**

(b) What is the most likely sequence of tags? **(1pt)**

**Problem 2: Forward Algorithm.**

(a) Using the matrices given in problem 1, compute by hand the forward path probability trellis for the sentence “Dumbledore fed his phoenix peanuts”. **(3pts)**

(b) What is the probability of the sentence? **(1pt)**

**Problem 3: Context Free Parses**

Using the grammar rules listed in Section 12.3, draw parse trees for the following sentences. Don’t worry about agreement, tense, or aspect. Give only a single parse for each sentence, but clearly indicate if the sentences are syntactically ambiguous, and why. If you must add a rule to complete a parse, clearly indicate what rule you have added. Ignore punctuation. **(2pts)**

(a) Wild deer kills man with rifle.

(b) The horse the dog raced past the barn fell.

(c) I wish running to catch the bus wasn’t an everyday occurrence, but it is.

(d) Ben and Alyssa went to the grocery store hoping to buy groceries for dinner.

(FOR NPL I NEED 2 COPIES FOR 2 STUDENTS NO PLAGIARIASM)