0. nginx_setup.sh

# Nginx can serve FLV/MP4 files by pseudo-streaming way without any specific media-server software. 
# To do the custom build we use 2 modules: --with-http_secure_link_module --with-http_flv_module
# This module "secure-link" helps you to protect links from stealing away.
#
# NOTE: see more details at coderwall: http://coderwall.com/p/3hksyg

cd /usr/src
wget http://nginx.org/download/nginx-1.5.13.tar.gz
tar xzvf ./nginx-1.5.13.tar.gz && rm -f ./nginx-1.5.13.tar.gz

wget ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-8.32.tar.gz
tar xzvf pcre-8.32.tar.gz && rm -f ./pcre-8.32.tar.gz

wget http://www.openssl.org/source/openssl-1.0.1g.tar.gz
tar xzvf openssl-1.0.1g.tar.gz && rm -f openssl-1.0.1g.tar.gz

cd nginx-1.5.13 && ./configure --prefix=/opt/nginx --with-pcre=/usr/src/pcre-8.32 --with-openssl-opt=no-krb5 --with-openssl=/usr/src/openssl-1.0.1g --with-http_ssl_module --without-mail_pop3_module --without-mail_smtp_module --without-mail_imap_module --with-http_stub_status_module --with-http_secure_link_module --with-http_flv_module --with-http_mp4_module
make && make install

1. misc_setup.sh

$ cd /opt/nginx/html
$ echo "<cross-domain-policy>
   <allow-access-from domain='*.your_domain.com' />
</cross-domain-policy>" > crossdomain.xml

$ echo "User-Agent: *
Disallow: /" > robots.txt

2. nginx.conf

# Nginx uses the protected links that build with md5 of YOUR_SECRET_PASSWORD_HERE, URI and Unix timestamp

user                            app;
worker_processes                2;
timer_resolution                100ms;
error_log                       logs/error.log;
pid                             logs/nginx.pid;

events {
    worker_connections          1024;
}


http {
    include                     mime.types;
    default_type                application/octet-stream;

    access_log                  off;
    sendfile                    on;
    server_tokens               off;
    keepalive_timeout           65;

    ssl_certificate             /opt/nginx/ssl_certs/server.crt;
    ssl_certificate_key         /opt/nginx/ssl_certs/server.key;
    ssl_session_timeout         15m;
    ssl_protocols               SSLv3 TLSv1 TLSv1.1 TLSv1.2;
    ssl_prefer_server_ciphers   on;
    ssl_session_cache           shared:SSL:10m;


    server {
      	ssl                     on;
        listen                  443 default ssl;
        access_log              logs/access.log;

        location /video/ {
          rewrite               /video/([a-zA-Z0-9_\-]*)/([0-9]*)/(.*)\.flv$ /flv/$3.flv?st=$1&e=$2;
        }

        location /flv/ {
          internal;
          secure_link           $arg_st,$arg_e;
          secure_link_md5       YOUR_SECRET_PASSWORD_HERE$arg_e$uri;

          if ($secure_link = "")  { return 403; }
          if ($secure_link = "0") { return 403; }

          root                  /mnt/your_directory;
          flv;

          add_header            Cache-Control  'private, max-age=0, must-revalidate';
          add_header            Strict-Transport-Security "max-age=16070400; includeSubdomains";
          add_header            X-Frame-Options DENY;
        }

        location =/ {
          root                  /404.html;
        }

        location = /50x.html {
          root                  html;
        }

        location ~ \.(php|html)$ {
          deny                  all;
        }

    }
}

3. signature.rb

require 'rubygems'
require 'activesupport'
require 'digest/md5'

class Signature
  PASSWORD    = 'YOUR_SECRET_PASSWORD_HERE'   # use this password for nginx directive "secure_link_md5"
  DIR         = 'flv'                         # the internal nginx location to access to media files
  SERVER_NAME = 'http://your_server.com:8080' # nginx listen address and port
  attr_reader :expiration_time, :file_name, :md5

  def initialize(file_name)
    @expiration_time = (Time.now + 2.hours).to_i
    @file_name       = file_name
    md5_calculate
  end

  def generate
    # nginx secured URL to access to media files, "video" is the location, not real directory on filesystem
    "#{SERVER_NAME}/video/#{@md5}/#{expiration_time}/#{file_name}"
  end


  private

  def md5_calculate
    s    = "#{PASSWORD}#{@expiration_time}/#{DIR}/#{@file_name}"
    a    = Base64.encode64(Digest::MD5.digest(s))
    @md5 = a.tr("+/", "-_").sub('==', '').chomp
  end
end


url = Signature.new('video1.flv')
puts url.expiration_time #=> 1326559618
puts url.md5             #=> HLz1px_YzSNcbcaskzA6nQ
puts url.generate        #=> http://your_server.com:8080/video/HLz1px_YzSNcbcaskzA6nQ/1326559618/video1.flv