djego · September 30, 2017 23:20 · vishal007-0 · Sep 29, 2021 · OthTazi · Oct 28, 2021
diff --git a/rsa.py b/rsa.py
 '''
 620031587
 Net-Centric Computing Assignment
 Part A - RSA Encryption
 '''

 import random


 '''
 Euclid's algorithm for determining the greatest common divisor
 Use iteration to make it faster for larger integers
 '''
 def gcd(a, b):
    while b != 0:
        a, b = b, a % b
    return a

 '''
 Euclid's extended algorithm for finding the multiplicative inverse of two numbers
 '''
 def multiplicative_inverse(e, phi):
    d = 0
    x1 = 0
    x2 = 1
    y1 = 1
    temp_phi = phi
    
    while e > 0:
        temp1 = temp_phi/e
        temp2 = temp_phi - temp1 * e
        temp_phi = e
        e = temp2
        
        x = x2- temp1* x1
        y = d - temp1 * y1
        
        x2 = x1
        x1 = x
        d = y1
        y1 = y
    
    if temp_phi == 1:
        return d + phi

 '''
 Tests to see if a number is prime.
 '''
 def is_prime(num):
    if num == 2:
        return True
    if num < 2 or num % 2 == 0:
        return False
    for n in xrange(3, int(num**0.5)+2, 2):
        if num % n == 0:
            return False
    return True

 def generate_keypair(p, q):
    if not (is_prime(p) and is_prime(q)):
        raise ValueError('Both numbers must be prime.')
    elif p == q:
        raise ValueError('p and q cannot be equal')
    #n = pq
    n = p * q

    #Phi is the totient of n
    phi = (p-1) * (q-1)

    #Choose an integer e such that e and phi(n) are coprime
    e = random.randrange(1, phi)

    #Use Euclid's Algorithm to verify that e and phi(n) are comprime
    g = gcd(e, phi)
    while g != 1:
        e = random.randrange(1, phi)
        g = gcd(e, phi)

    #Use Extended Euclid's Algorithm to generate the private key
    d = multiplicative_inverse(e, phi)
    
    #Return public and private keypair
    #Public key is (e, n) and private key is (d, n)
    return ((e, n), (d, n))

 def encrypt(pk, plaintext):
    #Unpack the key into it's components
    key, n = pk
    #Convert each letter in the plaintext to numbers based on the character using a^b mod m
    cipher = [(ord(char) ** key) % n for char in plaintext]
    #Return the array of bytes
    return cipher

 def decrypt(pk, ciphertext):
    #Unpack the key into its components
    key, n = pk
    #Generate the plaintext based on the ciphertext and key using a^b mod m
    plain = [chr((char ** key) % n) for char in ciphertext]
    #Return the array of bytes as a string
    return ''.join(plain)
    

 if __name__ == '__main__':
    '''
    Detect if the script is being run directly by the user
    '''
    print "RSA Encrypter/ Decrypter"
    p = int(raw_input("Enter a prime number (17, 19, 23, etc): "))
    q = int(raw_input("Enter another prime number (Not one you entered above): "))
    print "Generating your public/private keypairs now . . ."
    public, private = generate_keypair(p, q)
    print "Your public key is ", public ," and your private key is ", private
    message = raw_input("Enter a message to encrypt with your private key: ")
    encrypted_msg = encrypt(private, message)
    print "Your encrypted message is: "
    print ''.join(map(lambda x: str(x), encrypted_msg))
    print "Decrypting message with public key ", public ," . . ."
    print "Your message is:"
    print decrypt(public, encrypted_msg)
	'''
	620031587
	Net-Centric Computing Assignment
	Part A - RSA Encryption
	'''

	import random


	'''
	Euclid's algorithm for determining the greatest common divisor
	Use iteration to make it faster for larger integers
	'''
	def gcd(a, b):
	while b != 0:
	a, b = b, a % b
	return a

	'''
	Euclid's extended algorithm for finding the multiplicative inverse of two numbers
	'''
	def multiplicative_inverse(e, phi):
	d = 0
	x1 = 0
	x2 = 1
	y1 = 1
	temp_phi = phi

	while e > 0:
	temp1 = temp_phi/e
	temp2 = temp_phi - temp1 * e
	temp_phi = e
	e = temp2

	x = x2- temp1* x1
	y = d - temp1 * y1

	x2 = x1
	x1 = x
	d = y1
	y1 = y

	if temp_phi == 1:
	return d + phi

	'''
	Tests to see if a number is prime.
	'''
	def is_prime(num):
	if num == 2:
	return True
	if num < 2 or num % 2 == 0:
	return False
	for n in xrange(3, int(num**0.5)+2, 2):
	if num % n == 0:
	return False
	return True

	def generate_keypair(p, q):
	if not (is_prime(p) and is_prime(q)):
	raise ValueError('Both numbers must be prime.')
	elif p == q:
	raise ValueError('p and q cannot be equal')
	#n = pq
	n = p * q

	#Phi is the totient of n
	phi = (p-1) * (q-1)

	#Choose an integer e such that e and phi(n) are coprime
	e = random.randrange(1, phi)

	#Use Euclid's Algorithm to verify that e and phi(n) are comprime
	g = gcd(e, phi)
	while g != 1:
	e = random.randrange(1, phi)
	g = gcd(e, phi)

	#Use Extended Euclid's Algorithm to generate the private key
	d = multiplicative_inverse(e, phi)

	#Return public and private keypair
	#Public key is (e, n) and private key is (d, n)
	return ((e, n), (d, n))

	def encrypt(pk, plaintext):
	#Unpack the key into it's components
	key, n = pk
	#Convert each letter in the plaintext to numbers based on the character using a^b mod m
	cipher = [(ord(char) ** key) % n for char in plaintext]
	#Return the array of bytes
	return cipher

	def decrypt(pk, ciphertext):
	#Unpack the key into its components
	key, n = pk
	#Generate the plaintext based on the ciphertext and key using a^b mod m
	plain = [chr((char ** key) % n) for char in ciphertext]
	#Return the array of bytes as a string
	return ''.join(plain)


	if __name__ == '__main__':
	'''
	Detect if the script is being run directly by the user
	'''
	print "RSA Encrypter/ Decrypter"
	p = int(raw_input("Enter a prime number (17, 19, 23, etc): "))
	q = int(raw_input("Enter another prime number (Not one you entered above): "))
	print "Generating your public/private keypairs now . . ."
	public, private = generate_keypair(p, q)
	print "Your public key is ", public ," and your private key is ", private
	message = raw_input("Enter a message to encrypt with your private key: ")
	encrypted_msg = encrypt(private, message)
	print "Your encrypted message is: "
	print ''.join(map(lambda x: str(x), encrypted_msg))
	print "Decrypting message with public key ", public ," . . ."
	print "Your message is:"
	print decrypt(public, encrypted_msg)
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