codebusters-ciphers/nihilist.py at main · NajmKHoda/codebusters-ciphers · GitHub

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from string import ascii_uppercase
alphabet = list(ascii_uppercase)

# Searches for a letter in a Polybius square and returns its index
def search_polybius(letter, polybius):
    for r, row in enumerate(polybius):
        for c, item in enumerate(row):
            if (letter in item): # We use "in" because of the special case of I/J
                return (r + 1)*10 + (c + 1)
    return -1 # If the letter isn't found for some reason

# Prompt the user for the first key
print("Please input the first key to be used.")
key_1 = input().upper()

# Create the Polybius square
polybius = [["" for x in range(5)] for y in range(5)]
r = 0
c = 0
used_letters = []

# First, fill the square with letters from the key
for char in key_1:
    if (char.isalpha() and char not in used_letters):
        # Special case of I/J
        if (char == "I" or char == "J"):
            polybius[r][c] = "I/J"
            used_letters.append("I")
            used_letters.append("J")
        else:
            polybius[r][c] = char
            used_letters.append(char)
        c = (c + 1) % 5
        if (c == 0):
            r += 1
            if (r > 4):
                break

# Then, fill in the rest of the letters
if (r <= 4):
    for char in alphabet:
        if (char not in used_letters):
            # Special case of I/J
            if (char == "I" or char == "J"):
                polybius[r][c] = "I/J"
                used_letters.append("I")
                used_letters.append("J")
            else:
                polybius[r][c] = char
            c = (c + 1) % 5
            if (c == 0):
                r += 1

# Print the Polybius square in a readable format
print("The Polybius square generated by this key is:")

# Print the first line w/ column numbers
print("   " + "  ".join([str(i) for i in range(1,6)]))

# Print the individual rows
for row_num, row in enumerate(polybius):
    row_output = str(row_num + 1) + " "
    for letter in row:
        if (letter == "I/J"):
            row_output += letter
        else:
            row_output += " {} ".format(letter)
    print(row_output)

# Prompt the user for the second input
print("Please input the second key to be used. This must contain at least one letter.")
valid = False
key_2 = ""
while (not valid):
    key_2 = input().upper()
    key_2 = "".join([x for x in key_2 if x.isalpha()])
    if (key_2 == ""):
        print("This does not contain at least one letter. Please try again.")
    else:
        valid = True

key_2_nums = [search_polybius(c, polybius) for c in key_2]

# Prompt the user for the message to encrypt
print("Please enter the message you want to encrypt. All characters that are not letters will be dropped.")
message = input().upper()
message = "".join([x for x in message if x.isalpha()])

# Get the cipher text
cipher_nums = []
for i, char in enumerate(message):
    key_num = key_2_nums[i % len(key_2_nums)]
    plain_num = search_polybius(char, polybius)
    cipher_nums.append(str(key_num + plain_num))

# Print the cipher text
print("The encrypted message is:")
print(" ".join(cipher_nums))