title: Can a deterministic hashing function be easily decrypted?
body: <blockquote>
    <p><strong>Possible Duplicates:</strong><br>
    <a href="https://stackoverflow.com/questions/1240852/is-it-possible-to-decrypt-md5-hashes">Is it possible to decrypt md5 hashes?</a><br>
    <a href="https://stackoverflow.com/questions/2235079/is-it-possible-to-reverse-a-sha1">Is it possible to reverse a sha1?</a>  </p>
  </blockquote>
  
  
  
  <p>i asked this question:
  <a href="https://stackoverflow.com/questions/3143693/working-with-huge-spreadsheet">working with HUGE spreadsheet</a></p>
  
  <p>and got a great answer and i followed the advice. i used this:
  <a href="http://splinter.com.au/blog/?p=86" rel="nofollow noreferrer">http://splinter.com.au/blog/?p=86</a></p>
  
  <p>and i hashed about 300,000 different elements in a column in an excel spreadsheet</p>
  
  <p>since you can do:</p>
  
  <pre><code>=SHA1HASH('The quick brown fox jumps over the lazy dog')
  </code></pre>
  
  <p>And you'd get back:</p>
  
  <pre><code>2fd4e1c67a2d28fced849ee1bb76e7391b93eb12
  </code></pre>
  
  <p>couldnt you go backwards as well?</p>
  
  <p>im saying if it encrypts the same text the same way every single time, what is the point?</p>
  
  <p>if you do know the hash algorithm, is it possible to go backwards?</p>
  
  <p>can you please explain to me very simply how does hashing work? how can you convert a 20gb to a 40 character hash? does it take a long time to hash a 20gb hardrive?</p>