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Task/RSA-code/Python/rsa-code-2.py

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+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])