title: A known-plaintext attack on an LFSR-based stream cipher
body: <p>I am reading a book about Cryptography, and I am stuck in a question. I am really trying to solve it for weeks. But I think the problem is I couldn't understand the whole picture. The question was like this :</p>
  
  <p>We conduct a known-plaintext attack on an LFSR-based stream cipher. We know that the plaintext sent was: </p>
  
  <p>1001 0010 0110 1101 1001 0010 0110</p>
  
  <p>By tapping the channel we observe the following stream:</p>
  
  <p>1011 1100 0011 0001 0010 1011 0001</p>
  
  <pre><code>1- What is the degree m of the key stream generator?
  2- What is the initialization vector?
  3- Determine the feedback coefficients of the LFSR.
  4- Draw a circuit diagram and verify the output sequence of the LFSR.
  </code></pre>
  
  <p>Many thanks for your help to me to understand cryptography and LFSR.</p>