Posted: August 6th, 2022

Programming Assigment 3

CWID: 50284838

Name: Pradhumna Gautam

import hashlib
import time
max_nonce = 2 ** 32 # 4 billion
def proof_of_work(header, difficulty_bits):
# calculate the difficulty target
target = 2 ** (256-difficulty_bits)
for nonce in range(max_nonce):
# define hash_result based on Problem1.a and Problem1.b
# hash_result

# check if this is a valid result, below the target
if int(hash_result, 16) < target: print("Success with nonce %d" % nonce) print("Hash is %s" % hash_result) return (hash_result,nonce) print("Failed after %d (max_nonce) tries" % nonce) return nonce if __name__ == '__main__': nonce = 0 hash_result = '' # difficulty from 0 to 31 bits for difficulty_bits in range(32): difficulty = 2 ** difficulty_bits print("Difficulty: %ld (%d bits)" % (difficulty, difficulty_bits)) print("Starting search...") # checkpoint the current time start_time = time.time() # make a new block which includes the hash from the previous block # we fake a block of transactions - just a string new_block = 'test block with transactions' + hash_result # find a valid nonce for the new block (hash_result, nonce) = proof_of_work(new_block, difficulty_bits) # checkpoint how long it took to find a result end_time = time.time() elapsed_time = end_time - start_time print("Elapsed Time: %.4f seconds" % elapsed_time) if elapsed_time > 0:
# estimate the hashes per second
hash_power = float(int(nonce)/elapsed_time)
print(“Hashing Power: %ld hashes per second” % hash_power)

CSCI 497 Assignment 03

30 points


• Show your work (at least 50% penalty otherwise)

• Submit a single Word ( or x) document containing all your answers to the
designated folder (“Assignment #3”) under Assignments (at least 10% penalty otherwise).
Neither PDF documents nor documents in other formats would be accepted.

• Make sure if you submitted the intended one. It is recommended that you download
what has been uploaded and double-check if the correct document has been submitted.

• You can submit as many times as you want, but the last submission will only be graded.
If the last submission is made after the deadline, there should be a late submission

• No plagiarism: Do not copy and paste any from textbooks and other resources to answer
questions (Zero will be given otherwise).

• No extension/resubmission request will be accepted.

Note: The instructor and TA will welcome your questions to clarify homework problems but do not
ask if what you answered is correct. We may not reply from Friday evening to Monday morning.

Problem 1 Proof-of-Work Algorithm and Hash Puzzle

As we have discussed in our lectures, Bitcoin achieves proof‐of‐work using hash puzzles. In
order to create a block, the node that proposes hat block is required to find a number, or
nonce , such that when you concatenate the nonce, the previous hash, and the list of
transactions that comprise that block and take the hash of this whole string, then that hash
output should be a number that falls into a target space that is quite small in relation to the
much larger output space of that hash function.

In this assignment, we will concentrate on a simple implementation of proof-of-work
algorithm and its improvement by addressing following questions.

a. Hash a string containing your CWID and full name using SHA-256 and show its hash
value containing only hexadecimal digits using the hexdigest() method included in the
module “hashlib”. Provide the source code, hash value, and the captured screenshot in
your submitted document.

Hashlib module:

b. Add a nonce (number) to the end of the string created in 1(a) and calculate the hash of
the input (string+nonce) by iterating the nonce (number) from 0 to 30. Provide the
source code and captured screenshot of program outputs in your submitted document.

c. Based on the implementation of a simplified proof-of-work algorithm is included in the
file””, set the string created in 1(a) in your new block and provide the
statement and captured screenshot in your submitted document.

d. Based on the changes made in 1(c), test the program. Provide the source code and
program output in your submitted document

e. Set the maximum difficulty (in bits) to 15 bits and maximum nonce to 2^{16}. Test the
program. Provide the source code and program output in your submitted document.

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