File rename

ciphers/caesar_cipher.py

@@ -0,0 +1,38 @@
+# The Caesar Cipher Algorithm
+
+message = input("Enter message: ")
+key = int(input("Key [1-26]: "))
+mode = input("Encrypt or Decrypt [e/d]: ")
+
+if mode.lower().startswith('e'):
+    mode = "encrypt"
+elif mode.lower().startswith('d'):
+    mode = "decrypt"
+
+LETTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+
+translated = ""
+
+message = message.upper()
+
+for symbol in message:
+    if symbol in LETTERS:
+        num = LETTERS.find(symbol)
+        if mode == "encrypt":
+            num = num + key
+        elif mode == "decrypt":
+            num = num - key
+
+        if num >= len(LETTERS):
+            num = num - len(LETTERS)
+        elif num < 0:
+            num = num + len(LETTERS)
+
+        translated = translated + LETTERS[num]
+    else:
+        translated = translated + symbol
+
+if mode == "encrypt":
+    print("Encryption:", translated)
+elif mode == "decrypt":
+    print("Decryption:", translated)

ciphers/simple_substitution_cipher.py

@@ -0,0 +1,62 @@
+import sys, random
+
+LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+
+def main():
+    message = input('Enter message: ')
+    key = 'LFWOAYUISVKMNXPBDCRJTQEGHZ'
+    resp = input('Encrypt/Decrypt [e/d]: ')
+
+    checkValidKey(key)
+
+    if resp.lower().startswith('e'):
+        mode = 'encrypt'
+        translated = encryptMessage(key, message)
+    elif resp.lower().startswith('d'):
+        mode = 'decrypt'
+        translated = decryptMessage(key, message)
+
+    print('\n%sion: \n%s' % (mode.title(), translated))
+    
+def checkValidKey(key):
+    keyList = list(key)
+    lettersList = list(LETTERS)
+    keyList.sort()
+    lettersList.sort()
+
+    if keyList != lettersList:
+        sys.exit('Error in the key or symbol set.')
+
+def encryptMessage(key, message):
+    return translateMessage(key, message, 'encrypt')
+
+def decryptMessage(key, message):
+    return translateMessage(key, message, 'decrypt')
+
+def translateMessage(key, message, mode):
+    translated = ''
+    charsA = LETTERS
+    charsB = key
+
+    if mode == 'decrypt':
+        charsA, charsB = charsB, charsA
+        
+    for symbol in message:
+        if symbol.upper() in charsA:
+            symIndex = charsA.find(symbol.upper())
+            if symbol.isupper():
+                translated += charsB[symIndex].upper()
+            else:
+                translated += charsB[symIndex].lower()
+        else:
+            translated += symbol
+
+    return translated
+
+def getRandomKey():
+    key = list(LETTERS)
+    random.shuffle(key)
+    return ''.join(key)
+
+if __name__ == '__main__':
+    main()

ciphers/transposition_cipher.py

@@ -0,0 +1,43 @@
+import math
+
+def main():
+    message = input('Enter message: ')
+    key = int(input('Enter key [2-%s]: ' % (len(message) - 1)))
+    mode = input('Encryption/Decryption [e/d]: ')
+
+    if mode.lower().startswith('e'):
+        text = encryptMessage(key, message)
+    elif mode.lower().startswith('d'):
+        text = decryptMessage(key, message)
+
+    # Append pipe symbol (vertical bar) to identify spaces at the end.
+    print('Output:\n%s' %(text + '|'))
+
+def encryptMessage(key, message):
+    cipherText = [''] * key
+    for col in range(key):
+        pointer = col
+        while pointer < len(message):
+            cipherText[col] += message[pointer]
+            pointer += key
+    return ''.join(cipherText)
+
+def decryptMessage(key, message):
+    numCols = math.ceil(len(message) / key)
+    numRows = key
+    numShadedBoxes = (numCols * numRows) - len(message)
+    plainText = [""] * numCols
+    col = 0; row = 0;
+
+    for symbol in message:
+        plainText[col] += symbol
+        col += 1
+
+        if (col == numCols) or (col == numCols - 1) and (row >= numRows - numShadedBoxes):
+            col = 0
+            row += 1
+
+    return "".join(plainText)
+
+if __name__ == '__main__':
+    main()