title: Read a long file and use nodejs to crypt
body: <p>This is my first question. English is not my first language.
  I have a file that contains around 800K lines. I have to read and encrypt them using the sjcl library. Until now, the only thing I did is this lines:</p>
  
  <pre><code>var sjcl = require('sjcl/sjcl.js');
  var fs = require('fs'),
      readline = require('readline'),
      stream = require('stream');
  var instream = fs.createReadStream('data');
  var outstream = new stream;
  outstream.readable = true;
  outstream.writable = true;
  
  var rl = readline.createInterface({
      input: instream,
      output: outstream,
      terminal: false
  });
  
  rl.on('line', function(line) {
      var cred = line.toLowerCase()+line;
      var salt = sjcl.codec.utf8String.toBits(cred);
      var id = sjcl.misc.scrypt(cred,salt,2048,8,1,32);
      var ret = sjcl.codec.hex.fromBits(id);
      console.log(ret+":"+line);
      });
  </code></pre>
  
  <p>It works, but this is very slow(10 lines/sec). Is there any way to speed up the process?</p>