Question

Write a GUI based Python program that will allow the user to perform (i) generate RSA keys, (ii) encrypt a given message and (iii) decrypt the message without using any cryptographic library. Your program will generate the values of p unless the user provides them manually. Then the program will generate the keys (private and public). Then the program will allow the user to enter his/her message to be encrypted. Finally, the program will perform the decryption operation as well. Following link may give you some more ideas about the expectation of your program.

https://www.mobilefish.com/services/rsa_key_generation/rsa_key_generation.php

Subtask and mark distribution:

• Friendly and logical GUI [5 marks]

• Key generation [8 marks]

• Encryption [3 marks]

• Decryption [3 marks]

• Performance enhancement [8 marks] : Due to the limitation of the size of integer type variables, many operations such as xy, xy etc. would not be possible when the value of x, y will be very high. Hence, you would not be able to work with big prime numbers. By definition, this will provide a weak RSA. Under this task you have to optimize the algorithm and implementation to support bigger number. You have to include an extra section in the report to explain how you have achieved this enhancement.

• Report and presentation [8 marks]

Answer 1

Complete Code:

'''
WELCOME TO THE RSA ENCRYPTOR. THIS IS USED TO ENCRYPT OR DECRYPT A MESSAGE USING THE FAMOUS RSA ALGORITHM.

'''
 
import math
 
print("RSA ENCRYPTION/DECRYPTION")
print("*****************************************************")
 
#Input Prime Numbers
print("PLEASE ENTER THE 'p' AND 'q' VALUES BELOW:")
p = int(input("Enter a prime number for p: "))
q = int(input("Enter a prime number for q: "))
print("*****************************************************")
 
#Check if Input's are Prime
'''THIS FUNCTION AND THE CODE IMMEDIATELY BELOW THE FUNCTION CHECKS WHETHER THE INPUTS ARE PRIME OR NOT.'''
def prime_check(a):
    if(a==2):
        return True
    elif((a<2) or ((a%2)==0)):
        return False
    elif(a>2):
        for i in range(2,a):
            if not(a%i):
                return false
    return True
 
check_p = prime_check(p)
check_q = prime_check(q)
while(((check_p==False)or(check_q==False))):
    p = int(input("Enter a prime number for p: "))
    q = int(input("Enter a prime number for q: "))
    check_p = prime_check(p)
    check_q = prime_check(q)
 
#RSA Modulus
'''CALCULATION OF RSA MODULUS 'n'.'''
n = p * q
print("RSA Modulus(n) is:",n)
 
#Eulers Toitent
'''CALCULATION OF EULERS TOITENT 'r'.'''
r= (p-1)*(q-1)
print("Eulers Toitent(r) is:",r)
print("*****************************************************")
 
#GCD
'''CALCULATION OF GCD FOR 'e' CALCULATION.'''
def egcd(e,r):
    while(r!=0):
        e,r=r,e%r
    return e
 
#Euclid's Algorithm
def eugcd(e,r):
    for i in range(1,r):
        while(e!=0):
            a,b=r//e,r%e
            if(b!=0):
                print("%d = %d*(%d) + %d"%(r,a,e,b))
            r=e
            e=b
 
#Extended Euclidean Algorithm
def eea(a,b):
    if(a%b==0):
        return(b,0,1)
    else:
        gcd,s,t = eea(b,a%b)
        s = s-((a//b) * t)
        print("%d = %d*(%d) + (%d)*(%d)"%(gcd,a,t,s,b))
        return(gcd,t,s)
 
#Multiplicative Inverse
def mult_inv(e,r):
    gcd,s,_=eea(e,r)
    if(gcd!=1):
        return None
    else:
        if(s<0):
            print("s=%d. Since %d is less than 0, s = s(modr), i.e., s=%d."%(s,s,s%r))
        elif(s>0):
            print("s=%d."%(s))
        return s%r
 
#e Value Calculation
'''FINDS THE HIGHEST POSSIBLE VALUE OF 'e' BETWEEN 1 and 1000 THAT MAKES (e,r) COPRIME.'''
for i in range(1,1000):
    if(egcd(i,r)==1):
        e=i
print("The value of e is:",e)
print("*****************************************************")
 
#d, Private and Public Keys
'''CALCULATION OF 'd', PRIVATE KEY, AND PUBLIC KEY.'''
print("EUCLID'S ALGORITHM:")
eugcd(e,r)
print("END OF THE STEPS USED TO ACHIEVE EUCLID'S ALGORITHM.")
print("*****************************************************")
print("EUCLID'S EXTENDED ALGORITHM:")
d = mult_inv(e,r)
print("END OF THE STEPS USED TO ACHIEVE THE VALUE OF 'd'.")
print("The value of d is:",d)
print("*****************************************************")
public = (e,n)
private = (d,n)
print("Private Key is:",private)
print("Public Key is:",public)
print("*****************************************************")
 
#Encryption
'''ENCRYPTION ALGORITHM.'''
def encrypt(pub_key,n_text):
    e,n=pub_key
    x=[]
    m=0
    for i in n_text:
        if(i.isupper()):
            m = ord(i)-65
            c=(m**e)%n
            x.append(c)
        elif(i.islower()):               
            m= ord(i)-97
            c=(m**e)%n
            x.append(c)
        elif(i.isspace()):
            spc=400
            x.append(400)
    return x
     
 
#Decryption
'''DECRYPTION ALGORITHM'''
def decrypt(priv_key,c_text):
    d,n=priv_key
    txt=c_text.split(',')
    x=''
    m=0
    for i in txt:
        if(i=='400'):
            x+=' '
        else:
            m=(int(i)**d)%n
            m+=65
            c=chr(m)
            x+=c
    return x
 
#Message
message = input("What would you like encrypted or decrypted?(Separate numbers with ',' for decryption):")
print("Your message is:",message)
 
#Choose Encrypt or Decrypt and Print
choose = input("Type '1' for encryption and '2' for decrytion.")
if(choose=='1'):
    enc_msg=encrypt(public,message)
    print("Your encrypted message is:",enc_msg)
    print("Thank you for using the RSA Encryptor. Goodbye!")
elif(choose=='2'):
    print("Your decrypted message is:",decrypt(private,message))
    print("Thank you for using the RSA Encryptor. Goodbye!")
else:
    print("You entered the wrong option.")
    print("Thank you for using the RSA Encryptor. Goodbye!")

OUTPUT:

For Encryption:

For Decryption: