title: Ruby: file encryption/decryption with private/public keys
body: <p>I am searching for an algorithm for file encryption/decryption which satisfies the following requirements:</p>
  
  <ul>
  <li>Algorithm must be reliable</li>
  <li>Algorithm should be fast for rather big files</li>
  <li>Private key can be generated by some parameter (for example, password)</li>
  <li>Generated private key must be compatible with public key (public key is generated only once and stored in database)</li>
  </ul>
  
  <p>Is there any Ruby implementation of suggested algorithms?</p>