import random


def propose_cipher(current_cipher):
	"""
	Proposes a new cipher by randomly swapping the place of two letters in the current cipher

	Inputs
	------
	current_cipher : a string, in which order matters, that is mapped to from the alphabet in the 
			 		 encrypted document i.e. abcdefg.. -> udhjenk...

	Returns
	-------
	a string, which is the new proposed cipher
	"""
	first_letter = random.choice(list(current_cipher))
	second_letter = random.choice(list(current_cipher))

	while(first_letter == second_letter):
		second_letter = random.choice(list(current_cipher))

	new_cipher = ""
	for c in current_cipher:
		if (c == first_letter):
			new_cipher += second_letter
		elif (c == second_letter):
			new_cipher += first_letter
		else:
			new_cipher+=c

	return new_cipher