Assignment 2 of Network Security ，taught by Dr.Hussein Abdel-Wahab

a2_1.ipynb

a2_2.ipynb

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    "This code implements the first round of IDEA.\n",
    "\n",
    "This python implementation follows the code notation of\n",
    "1.\n",
    "Dr.Wahab's lecture\n",
    "and\n",
    "2.\n",
    "[Rhee_Y] Internet_Security_Cryptographic_Principle\n",
    "[Bruce Schneier] Applied Cryptography\n",
    "Protocols, Algorithms, and Source Code in C\n",
    "\n",
    "Personally I think Bruce Schneier's method in his book # Chapter 13.9 \n",
    " simplifies the idea so that I can reuse the result computed before without violating anything in Dr.Wahab's notation.\n",
    " "
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     "text": [
      "0001000000000001\n",
      "00010000000000010001000111100111\n"
     ]
    }
   ],
   "source": [
    "# test input and key from fall 2014\n",
    "# The input  data block is: 0001 0001 0000 FFFF        &\n",
    "# The encryption key is:   FFFF 0000 0000 0001 0001 0001 0001 0001\n",
    "# input='0001 0001 0000 FFFF'.replace(' ','')\n",
    "# key='FFFF 0000 0000 0001 0001 0001 0001 0001'.replace(' ','')\n",
    "# Answer: 0002 FFFD FFFD  0003\n",
    "\n",
    "# test input and key from fall 2015\n",
    "input='0001 0000 0000 0001'.replace(' ','')\n",
    "key='0001 0000 0000 0001 0001 0001 1110 0111'.replace(' ','')\n",
    "print input\n",
    "print key\n"
   ]
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   "execution_count": 566,
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   "outputs": [
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     "name": "stdout",
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     "text": [
      "['0001', '0000', '0000', '0001', '0001', '0001']\n",
      "16\n",
      "['0000000000000001', '0000000000000000', '0000000000000000', '0000000000000001', '0000000000000001', '0000000000000001']\n"
     ]
    }
   ],
   "source": [
    "# # key\n",
    "# tokenize the key into 6 groups,each 4 hex digits\n",
    "z=[]\n",
    "for i in range(6):\n",
    "    z.append(key[4*i:4*i+4])\n",
    "print z\n",
    "# convert the 4 hex digits to 16 bit binary string\n",
    "for i in range(6):\n",
    "    z[i]=\"{0:016b}\".format(int(z[i], 16))\n",
    "#     z[i]=bin(int(z[i], 16))\n",
    "print len(z[0])\n",
    "print z\n",
    "\n"
   ]
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   "execution_count": 567,
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "['0001', '0000', '0000', '0001']\n"
     ]
    }
   ],
   "source": [
    "# plain text\n",
    "x=[]\n",
    "x.append(input[0:4])\n",
    "x.append(input[4:8])\n",
    "x.append(input[8:12])\n",
    "x.append(input[12:16])\n",
    "print x\n"
   ]
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  {
   "cell_type": "code",
   "execution_count": 568,
   "metadata": {
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "['0000000000000001', '0000000000000000', '0000000000000000', '0000000000000001']\n",
      "['0000000000000001', '0000000000000000', '0000000000000000', '0000000000000001', '0000000000000001', '0000000000000001']\n"
     ]
    }
   ],
   "source": [
    "# hex to binary\n",
    "\n",
    "for i in range(len(x)):\n",
    "#     x[i]=\"{0:016b}\".format(int(x[i], 16))\n",
    "# hex to int, \n",
    "# then int to binary\n",
    "#     bstr=\"{0:016b}\".format(int(x[i], 16))\n",
    "#     x[i]=bin(int(bstr, 2))\n",
    "    x[i]=\"{0:016b}\".format(int(x[i], 16))\n",
    "print x\n",
    "print z"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 569,
   "metadata": {
    "collapsed": false
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   "outputs": [
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     "text": [
      "0000000000000001\n",
      "0000000000000001\n",
      "\n",
      "the final answer given the input \n",
      "0001000000000001\n",
      "and key \n",
      "00010000000000010001000111100111\n",
      " is: \n",
      "0x3 0x2 0x3 0x2\n"
     ]
    }
   ],
   "source": [
    "print z[0]\n",
    "print x[0]\n",
    "print \n",
    "# Bruce Schneier's method in his book Chapter 13.9 \n",
    "r1=( int(x[0],2)*int(z[0],2) )%(2**16+1)\n",
    "r2=( int(x[1],2)+int(z[1],2) )%(2**16)\n",
    "r3=( int(x[2],2)+int(z[2],2) )%(2**16)\n",
    "r4=( int(x[3],2)*int(z[3],2) )%(2**16+1)\n",
    "r5=r1^r3\n",
    "r6=r2^r4\n",
    "r7=(r5* int(z[4],2))%(2**16+1)\n",
    "r8= (r6+r7)%(2**16)\n",
    "r9=r8*int(z[5],2)%(2**16+1)\n",
    "r10= (r7+r9)%(2**16)\n",
    "r11= r1^r9\n",
    "r12= r3^r9\n",
    "r13= r2^r10\n",
    "r14= r4^r10\n",
    "print 'the final answer given the input '\n",
    "print input\n",
    "print 'and key '\n",
    "print key\n",
    "print ' is: '\n",
    "# print r1,r2,r3,r4,r5,r6,r7,r8,r9,r10,r11,r12,r13,r14\n",
    "# Answer for Fall2014: 0002 FFFD FFFD  0003\n",
    "#below is the answer for the given input\n",
    "# choose the input to be the one for FALL2014,I have the same answer\n",
    "# So I believe my answer is correct for FALL2015 input\n",
    "print hex(r11),hex(r12),hex(r13),hex(r14)"
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a2_3.ipynb