RSA code: Difference between revisions

{{Needs-review}}

This code will open up a simple Tkinter window which has space to type a message. That message can then be encrypted by pressing the button labeled "encrypt". It will then print an output of ciphertext

blocks, separated by commas. To decrypt a message, simply press the decrypt button. All ciphertext data must be entered with each block separated by commas. The ciphertext always goes (and appears)

in the bottom box, while plaintext goes (and appears) in the topmost box. Upon decryption, random letters may have been appended to the end of the message, this is an aspect of the code to ensure the final

block of plaintext is not a single letter, for example, a, 01, encoded is 01 (which means this letter was transmitted in the open!).

Note: the key given here is a toy key, it is easily broken.

<lang python>from tkinter import *

import random

import time

letter = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q",

"r","s","t","u","v","w","x","y","z",",",".","!","?",' ']

number = ["01","02","03","04","05","06","07","08","09","10","11","12","13",

"14","15","16","17","18","19","20","21","22","23","24","25","26","27",

"28","29","30",'31']

n = 2537

e = 13

d = 937

def decrypt(F,d):

# performs the decryption function on an block of ciphertext

if d == 0:

return 1

if d == 1:

return F

w,r = divmod(d,2)

if r == 1:

return decrypt(F*F%n,w)*F%n

else:

return decrypt(F*F%n,w)

def correct():

# Checks to see if the numerical ciphertext block should have started with a 0 (by seeing if the 0 is missing), if it is, it then adds the 0.

# example - 0102 is output as 102, which would lead the computer to think the first letter is 10, not 01. This ensures this does not happen.

for i in range(len(D)):

if len(str(P[i]))%2 !=0:

y = str(0)+str(P[i])

P.remove(str(P[i]))

P.insert(i,y)

def cipher(b,e):

# Performs the Encryption function on a block of ciphertext

if e == 0:

return 1

if e == 1:

return b

w,r = divmod(e,2)

if r == 1:

return cipher(b*b%n,w)*b%n

else:

return cipher(b*b%n,w)

def group(j,h,z):

# Places the plaintext numbers into blocks for encryption

for i in range(int(j)):

y = 0

for n in range(h):

y += int(numP[(h*i)+n])*(10**(z-2*n))

X.append(int(y))

class App:

# Creates a Tkineter window, for ease of operation

def __init__(self, master):

frame = Frame(master)

frame.grid()

#create a button with the quit command, and tell it where to go

quitbutton = Button(frame, text = "quit", fg ="red",

command = root.quit, width = 10)

quitbutton.grid(row = 0, column =3)

#create an entry box, tell it where it goes, and how large it is

entry = Entry(frame, width = 100)

entry.grid(row = 0, column = 0)

#set initial content of the entry box

self.contents = StringVar()

self.contents.set("Type message here")

entry["textvariable"] = self.contents

# Create a button which initializes the decryption of ciphertext

decrypt = Button(frame,text = "Decrypt", fg = "blue",

command = self.Decrypt)

decrypt.grid(row = 2, column = 1)

#create a label to display the number of ciphertext blocks in an encoded message

label = Label(frame, text = "# of blocks")

label.grid(row = 1, column = 1)

#creates a button which initializes the encryption of plaintext

encrypt = Button(frame, text="Encrypt", fg = "blue",

command = self.Encrypt)

encrypt.grid(row =0, column =1)

#create an entry box for the value of "n"

nbox = Entry(frame, width = 100)

nbox.grid(row = 3, column = 0)

self.n = StringVar()

self.n.set(n)

nbox["textvar"] = self.n

nbox.bind('<Key-Return>', self.set_n) #key binding, when you press "return", the value of "n" is changed to the value now in the box

nlabel = Label(frame, text = "the value of 'n'")

nlabel.grid(row = 3, column = 1)

#create an entry box for the value of "e"

ebox = Entry(frame, width = 100)

ebox.grid(row = 4, column = 0)

self.e = StringVar()

self.e.set(e)

ebox["textvar"] = self.e

ebox.bind('<Key-Return>', self.set_e)

elabel = Label(frame, text = "the value of 'e'")

elabel.grid(row = 4, column = 1)

#create an entry box for the value of "d"

dbox = Entry(frame, width = 100)

dbox.grid(row =5, column = 0)

self.d = StringVar()

self.d.set(d)

dbox["textvar"] = self.d

dbox.bind('<Key-Return>', self.set_d)

dlabel = Label(frame, text = "the value of 'd'")

dlabel.grid(row = 5, column =1)

blocks = Label(frame, width = 100)

blocks.grid(row = 1, column =0)

self.block = StringVar()

self.block.set("number of blocks")

blocks["textvar"] = self.block

output = Entry(frame, width = 100)

output.grid(row = 2, column = 0)

self.answer = StringVar()

self.answer.set("Ciphertext")

output["textvar"] = self.answer

# The commands of all the buttons are defined below

def set_n(self,event):

global n

n = int(self.n.get())

print("n set to", n)

def set_e(self, event):

global e

e = int(self.e.get())

print("e set to",e)

def set_d(self,event):

global d

d = int(self.d.get())

print("d set to", d)

def Decrypt(self):

#decrypts an encoded message

global m,P,D,x,h,p,Text,y,w,PText

P = []

D = str(self.answer.get()) #Pulls the ciphertext out of the ciphertext box

D = D.lstrip('[') #removes the bracket "[" from the left side of the string

D = D.rstrip(']')

D = D.split(',') #splits the string into a list of strings, separating at each comma.

for i in range(len(D)): #decrypts each block in the list of strings "D"

x = decrypt(int(D[i]),d)

P.append(str(x))

correct() #ensures each block is not missing a 0 at the start

h = len(P[0])

p = []

for i in range(len(D)): #further separates the list P into individual characters, i.e. "0104" becomes "01,04"

for n in range(int(h/2)):

p.append(str(P[i][(2*n):((2*n)+2)])) # grabs every 2 character group from the larger block. It gets characters between 2*n, and (2*n)+2, i.e. characters 0,1 then 2,3 etc...

Text = []

for i in range(len(p)): # converts each block back to text characters

for j in range(len(letter)):

if str(p[i]) == number[j]:

Text.append(letter[j])

PText = str()

for i in range(len(Text)): #places all text characters in one string

PText = PText + str(Text[i])

self.contents.set(str(PText)) #places the decrypted plaintext in the plaintext box

def Encrypt(self):

#encrypts a plaintext message using the current key

global plaintext,numP,q,j,z,X,C

plaintext = self.contents.get() #pulls the plaintext out of the entry box for use

plaintext = plaintext.lower() #places all plaintext in lower case

numP = []

for i in range(len(plaintext)): # converts letters and symbols to their numerical values

for j in range(len(letter)):

if plaintext[i] == letter[j]:

numP.append(number[j])

h = (len(str(n))//2)-1 # This sets the block length for the code in question, based on the value of "n"

q = len(numP)%h

for i in range(h-q):

numP.append(number[random.randint(0,25)]) # Ensures the final block of plaintext is filled with letters, and is not a single orphaned letter.

j = len(numP) / h

X = []

z = 0

for m in range(h-1):

z+=2

group(j,h,z) # This sets the numerical plaintext into blocks of appropriate size, and places them in the list "X"

k = len(X)

C = []

for i in range(k): # performs the cipher function for each block in the list of plaintext blocks

b = X[i]

r = cipher(b,e)

C.append(r)

self.answer.set(C)

self.block.set(len(C)) #places the ciphertext into the ciphertext box

root = Tk()

app = App(root)

root.mainloop()

root.destroy()</lang>

Alternatively, a version without the tkinter window, which uses the same components as the program above, only without the Tkinter interface.

<lang python>import random

import time

def decrypt(F,d):

if d == 0:

return 1

if d == 1:

return F

w,r = divmod(d,2)

if r == 1:

return decrypt(F*F%n,w)*F%n

else:

return decrypt(F*F%n,w)

def correct():

for i in range(len(C)):

if len(str(P[i]))%2 !=0:

y = str(0)+str(P[i])

P.remove(str(P[i]))

P.insert(i,y)

def cipher(b,e):

if e == 0:

return 1

if e == 1:

return b

w,r = divmod(e,2)

if r == 1:

return cipher(b*b%n,w)*b%n

else:

return cipher(b*b%n,w)

def group(j,h,z):

for i in range(int(j)):

y = 0

for n in range(h):

y += int(numP[(h*i)+n])*(10**(z-2*n))

X.append(int(y))

def gcd(a, b):

while b != 0:

(a, b) = (b, a%b)

return a

letter = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q",

"r","s","t","u","v","w","x","y","z",",",".","!","?"," "]

number = ["01","02","03","04","05","06","07","08","09","10","11","12","13",

"14","15","16","17","18","19","20","21","22","23","24","25","26","27",

"28","29","30","31"]

print( '\n' )

def Decrypt():

#decrypts an encoded message

global m,P,C,x,h,p,Text,y,w

P = []

C = str(input("Enter ciphertext blocks:"))

C = C.lstrip('[')

C = C.rstrip(']')

C = C.split(',')

for i in range(len(C)):

x = decrypt(int(C[i]),d)

P.append(str(x))

correct()

#print(P)

h = len(P[0])

p = []

for i in range(len(C)):

for n in range(int(h/2)):

p.append(str(P[i][(2*n):((2*n)+2)]))

Text = []

for i in range(len(p)):

for j in range(len(letter)):

if str(p[i]) == number[j]:

Text.append(letter[j])

PText = str()

for i in range(len(Text)):

PText = PText + str(Text[i])

print("Plaintext is:", PText)

def Encrypt():

#encrypts a plaintext message using the current key

global plaintext,numP,q,j,z,X,C

plaintext =(input("Enter Plaintext :"))

plaintext = plaintext.lower()

numP = []

for i in range(len(plaintext)):

for j in range(len(letter)):

if plaintext[i] == letter[j]:

numP.append(number[j])

h = (len(str(n))//2)-1

q = len(numP)%h

for i in range(h-q):

numP.append(number[random.randint(0,25)])

j = len(numP) / h

#print(numP)

X = []

z = 0

for m in range(h-1):

z+=2

group(j,h,z)

k = len(X)

C = []

for i in range(k):

b = X[i]

r = cipher(b,e)

C.append(r)

print("Ciphertext:",C)

print("Number of Ciphertext blocks:",len(C))

def setup():

global n,e,d

while True:

try:

n = int(input(" Enter a value for n :"))

if n > 2:

break

except ValueError:

print('please enter a number')

while 1!=2 :

try:

e = int(input(" Enter a value for e :"))

if e >= 2:

break

except ValueError:

print('please enter a number')

while True:

try:

d = int(input(" Enter a value for d. If d unknown, enter 0 :"))

if d >= 0:

break

except ValueError:

print('please enter a number')

#setup()

n = 2537

e = 13

d = 937

print("To redefine n,e, or d, type 'n','e',... etc.")

print("To encrypt a message with the current key, type 'Encrypt'")

print("To decrypt a message with the current key, type 'Decrypt'")

print("Type quit to exit")

print( '\n' )

print( '\n' )

mm = str()

while mm != 'quit':

mm = input("Enter Command...")

if mm.lower() == 'encrypt':

Encrypt()

elif mm.lower() == 'decrypt':

Decrypt()

elif mm.lower() == 'n':

try:

print('current n = ',n)

n = int(input(" Enter a value for n :"))

except ValueError:

print('That is not a valid entry')

elif mm.lower() == 'help':

print("To redefine n,e, or d, type 'n','e',... etc.")

print("To encrypt a message with the current key, type 'Encrypt'")

print("To decrypt a message with the current key, type 'Decrypt'")

print("Type quit to exit")

print( '\n' )

print( '\n' )

elif mm.lower() == 'e':

try:

print('current e = ',e)

e = int(input(" Enter a value for e :"))

except ValueError:

print('That is not a valid entry')

elif mm.lower() == 'd':

try:

print('current d = ',d)

d = int(input(" Enter a value for d :"))

except ValueError:

print('That is not a valid entry')

else:

if mm != 'quit':

ii= random.randint(0,6)

statements = ["I sorry, Dave. I'm afraid i can't do that","I'm begging you....read the directions","Nah ahh ahh, didnt say the magic word","This input is....UNACCEPTABLE!!","Seriously....was that even a word???","Please follow the directions","Just type 'help' if you are really that lost"]

print(statements[ii])</lang>

Example use :

Any entered commands are '''not''' case sensitive, nor is the plaintext input. Commands must be spelled correctly. Ciphertext blocks are input all at once, but must be separated by commas. When decrypted, there may be random letters attached to the end of the message. The program does this in order to fill blocks completely, and not have orphaned characters.

<lang python>>>>

To redefine n,e, or d, type 'n','e',... etc.

To encrypt a message with the current key, type 'Encrypt'

To decrypt a message with the current key, type 'Decrypt'

Type quit to exit

Enter Command...ENCRYPT

Enter Plaintext :drink MORE Ovaltine

Ciphertext: [140, 2222, 1864, 1616, 821, 384, 2038, 2116, 2222, 205, 384, 2116, 45, 1, 2497, 793, 1864, 1616, 205, 41]

Number of Ciphertext blocks: 20

Enter Command...decrypt

Enter ciphertext blocks:[140, 2222, 1864, 1616, 821, 384, 2038, 2116, 2222, 205, 384, 2116, 45, 1, 2497, 793, 1864, 1616, 205, 41]

Plaintext is: drink more ovaltineu

Enter Command...quit

>>> </lang>