Question

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!")

this answer is posted by one of the expert and the issue is:

#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("*****************************************************")

this certain part doesn't execute as it shows the error that r is not defined. And Can you please provide the ans with indentation? im sure im making mistake in indentation. thanks

Answer 1

Answer:- With Indentation & Output Screenshot

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 Screenshot:-

Encryption of "data"

Description

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