As part of our goal to reduce the blockability of the proxies we host, we are now testing a new url encoding that uses a timestamp as the encryption key to encrypt proxied urls with RC4. You can try out a proxy using this encoding at http://test.polysolve.com.
The advantages of using RC4 encryption for urls, as opposed to more normal rot13 or hex encoding, is that for a given website you are visiting, the url used to reach that website is not always the same. This is important when you realize that all proxied urls contain an encoded version of “http”, which, with hex / rot13 encoding, always displays as “68747470″, which can easily be string matched by url filters, effectively blocking any proxy that uses hex / rot13, with a reletively low false positive rate.
In plain english, this means that it will be harder to make rules that effectively block all proxies, and instead admins and censors will have to block proxies on an individual basis, which is time consuming and error prone. Another win for anonymity and free speech!