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     "text": [
      "\n",
      "['e', 'f', 'g', 'f', 'o', 'e', 'u', 'i', 'f', 'f', 'b', 't', 'u', 'x', 'b', 'm', 'm', 'p', 'g', 'u', 'i', 'f', 'd', 'b', 't', 'u', 'm', 'f']\n",
      "\n"
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   "source": [
    "# ---------------------------------------------------------------\n",
    "# python best courses https://courses.tanpham.org/\n",
    "# ---------------------------------------------------------------\n",
    "# Write a Python program to create a Caesar encryption\n",
    "\n",
    "# Note : In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques.\n",
    "# It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet.\n",
    "# For example, with a left shift of 3, D would be replaced by A, E would become B, and so on.\n",
    "# The method is named after Julius Caesar, who used it in his private correspondence.\n",
    "\n",
    "# plaintext:  defend the east wall of the castle\n",
    "# ciphertext: efgfoe uif fbtu xbmm pg uif dbtumf\n",
    "\n",
    "def caesar_encrypt(realText, step):\n",
    "\toutText = []\n",
    "\tcryptText = []\n",
    "\t\n",
    "\tuppercase = ['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']\n",
    "\tlowercase = ['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']\n",
    "\n",
    "\tfor eachLetter in realText:\n",
    "\t\tif eachLetter in uppercase:\n",
    "\t\t\tindex = uppercase.index(eachLetter)\n",
    "\t\t\tcrypting = (index + step) % 26\n",
    "\t\t\tcryptText.append(crypting)\n",
    "\t\t\tnewLetter = uppercase[crypting]\n",
    "\t\t\toutText.append(newLetter)\n",
    "\t\telif eachLetter in lowercase:\n",
    "\t\t\tindex = lowercase.index(eachLetter)\n",
    "\t\t\tcrypting = (index + step) % 26\n",
    "\t\t\tcryptText.append(crypting)\n",
    "\t\t\tnewLetter = lowercase[crypting]\n",
    "\t\t\toutText.append(newLetter)\n",
    "\treturn outText\n",
    "\n",
    "code = caesar_encrypt('defend the east wall of the castle', 1)\n",
    "print()\n",
    "print(code)\n",
    "print()"
   ]
  }
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