Create RSA.py

Author: Compulytics

RSA.py

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+from random import randint, randrange
+def IS_PRIME(n):#Miller-Rabin primality check.
+	k=10
+	def check(a, s, d, n):
+		x = pow(a, d, n)
+		if x == 1:
+			return True
+		for i in xrange(s - 1):
+			if x == n - 1:
+				return True
+			x = pow(x, 2, n)
+		return x == n - 1
+	s = 0
+	d = n - 1
+
+	while d % 2 == 0:
+		d >>= 1
+		s += 1
+	for i in xrange(k):
+		a = randrange(2, n - 1)
+		if not check(a, s, d, n):
+			return False
+	return True
+def KEYGEN():
+	Key_P = randint(2**1023, 2**1024)#Initial pseudorandom value of P
+	Key_Q = randint(2**1020, 2**1021)#Initial pseudorandom value of Q
+	while not IS_PRIME(Key_P):#Primality check for P using IS_PRIME function
+		Key_P = randint(2**1023, 2**1024)#Recalculation of pseudorandom value of P if not prime.
+	while not IS_PRIME(Key_Q):#Primality check for Q using IS_PRIME function
+		Key_Q = randint(2**1023, 2**1024)#Recalculation of pseudorandom value of Q if not prime.
+	Key_N = Key_P * Key_Q#Calculation of n.
+	Key_PhiN = (Key_P - 1) * (Key_Q - 1)#Calculation of phi(n).
+	Key_E = randint(2, (Key_PhiN - 1))#Initial pseudorandom value of e.
+	while not IS_PRIME(Key_E):#Primality check for E using IS_PRIME function.
+		Key_E = randint(2, (Key_PhiN - 1))#Recalculation of pseudorandom value of e.
+	OldRemainder = Key_E#Set OldRemainder to be equil to e.
+	Remainder = Key_PhiN#Set Remainder to be equil to Phi of n.
+	i = 0#Bezout coefficient variable, inital value.
+	Oldi = 1#Previous value Bezout coefficient variable, inital value.
+	while Remainder:#While a non-zero remainder is found in the long division below.
+		OldRemainder, (Q, Remainder) = Remainder, divmod(OldRemainder, Remainder)#Paralell assignment of Q equals the quotient of the pair OldRemainder & Remainder via long division and OldRemainder now equals Remainder.
+		i, Oldi = Oldi - Q*i, i#Paralell assignment Oldi equals i and i equals Oldi minus Q multiplied by i.
+	Key_D = (Oldi % Key_PhiN)#Final calculation of d.
+	return (Key_N, Key_E, Key_D)#Return values to be used as private and public keys.
+def MAIN():
+	Plain_Text = "Hello World"#Plain text.
+	Bytes_Plain_Text = str.encode(Plain_Text)#Plain text converted to bytes.
+	Int_Plain_Text = int(Bytes_Plain_Text.encode('hex'), 16)#Plain text converted to Integer for printing.
+	Key_N, Key_E, Key_D = KEYGEN()#Generate RSA keys.
+MAIN()