PHP Encrypted Communication Between Servers

Encrypted Communication Between Websites

• Maintaining a central links list of all your sites
• Maintaining a central list of all your affiliate adverts for rotation
• Allowing content to be shared between sites
• Allowing content to be controlled/deleted from off site (ie a clients content) - this is useful for licensing.
• Encryption-server schemes where the encrypted key is held on a central site and client scripts use this server to encrypt messages without ever knowing the key.

These are just a few of the uses of this communication code. Here is a sample:

Inter-server Communications Code for Client

This function requests a file on a second server.
$filecontents=get_info("sitelinks.txt","http://www.mysite.com/transfer.php"); #sample call function get_info($filename,$masterurl){ $masterurl=$masterurl."?fname=$filename"; $transportkey='thekey'; $td = mcrypt_module_open(MCRYPT_DES, '', MCRYPT_MODE_ECB, ''); mcrypt_generic_init($td, $transportkey, 01234567); $curl_handle=curl_init(); curl_setopt($curl_handle,CURLOPT_URL,$masterurl); curl_setopt($curl_handle,CURLOPT_RETURNTRANSFER,1) ; $buffer = curl_exec($curl_handle); curl_close($curl_handle); $plaintext=urldecode(base64_decode(mdecrypt_generic ($td,$buffer))); return ($plaintext); }

This function serves a file to a requesting server.
$filename=$_GET['fname']; $iplist="~77.99.138.28~101.67.132.27~106.29.118.16~"; #list of ips that can be accepted if (! send_info("sitelinks.txt","http://www.mysite.com/transfer.php")){; #sample call echo "Bad Request } function send_info($filename,$iplist){ $transportkey='thekey'; $ip=$_SERVER['REMOTE_ADDR']; if (!(file_exists($filename))){ sleep(5); return false; } if (!(strpos("XX$iplist","~$ip~")){ sleep(20); return false; } #for security can only be called from allowed sites $plaintext=urlencode(file($filename)); $td = mcrypt_module_open(MCRYPT_DES, '', MCRYPT_MODE_ECB, ''); mcrypt_generic_init($td, $transportkey, 01234567); $encoded = mcrypt_generic ($td, $plaintext); $d2send=base64_encode($encoded); echo($d2send); return true; }

It is important that you check requesting sites to make sure they are ok. IP is a good way of doing this since it is difficult (not impossible) to spoof. These PHP routines are pretty secure since whoever tries to hack files from your site has to know the permissable IP(s) and also the transport key. To avoid an automated attack the program waits a few seconds before dying if the wrong info is given. Hopefully you will find this sample code useful, feel free to use any of our code snippets on your site it has been placed in a text box to make cut and paste easier. A link back to www.webmaster-a.com would be appreciated.!

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