diff --git a/docs/user/index.rst b/docs/user/index.rst index e8b5eb2..d494463 100644 --- a/docs/user/index.rst +++ b/docs/user/index.rst @@ -1,3 +1,41 @@ Introduction ============ +Censorship is the suppression of speech, public communication, or other information. +This may be done on the basis that such material is considered objectionable, harmful, sensitive, or "inconvenient". +Regardless of the reasons for censorship, the technical measures taken to implement it often look the same. +The *Bypass Censorship* portal provides a toolkit for circumventing censorship of Internet resources. +The circumvention methods available will often exploit either collateral freedom, traffic obfuscation, or both in order +to counter the measures put in place by the censor. + +Collateral Freedom +------------------ + +*Used by:* :doc:`Web Proxies `, :doc:`Tor Bridges ` + +"Collateral freedom" is an anti-censorship strategy that attempts to make it economically prohibitive for censors to +block an Internet resource. +The way in which a censor restricts access to resources will require knowing which content to block and which to allow. +It's incredibly difficult to achieve accuracy with filtering as the Internet is comprised of untagged free-form content +that must be categorised at speed. +This results in either over-blocking or under-blocking, and neither of these are desirable properties for the censor. + +This can be exploited by circumvention systems by deploying solutions at places that are "too big to block", like cloud +providers. +Either encryption or constantly rotating identifiers are then used to prevent censors from identifying requests for +censored information that is hosted among other content. +This forces censors to either allow access to the censored information or take down entire services. + +Traffic Obfuscation +------------------- + +*Used by:* :doc:`Tor Bridges ` + +"Traffic Obfuscation" is an anti-censorship strategy that attempts to make it difficult to fingerprint traffic. +This is more commonly used for general censorship circumvention solutions rather than means of accessing specific +resources. +There is a long tail of types of traffic on the Internet, including critical infrastructure communications like +industrial control systems, point-of-sale systems and security systems. +This can be exploited by circumvention systems by making their traffic look like one of these unclassified systems. +Not being able to accurately identify the traffic means that the cost of blocking access is unknown, and so it is more +difficult for a censor to justify the block. diff --git a/docs/user/lists.rst b/docs/user/lists.rst index f151579..99d454a 100644 --- a/docs/user/lists.rst +++ b/docs/user/lists.rst @@ -1,2 +1,2 @@ -Mirror Lists -============ +Distribution Lists +================== diff --git a/docs/user/proxies.rst b/docs/user/proxies.rst index b9f9a2e..851a3fe 100644 --- a/docs/user/proxies.rst +++ b/docs/user/proxies.rst @@ -1,2 +1,29 @@ Web Proxies -=========== \ No newline at end of file +=========== + +Web proxies provide alternate URLs to access censored resources. +These can be accessed through a normal web browser. +They use frequently changing URLs to evade censorship. +Some functionality on more complex websites may not work fully. +The URLs will have a limited lifetime as, once discovered, they can be blocked by censors. + +This assumption of a limited lifetime is built-in to the system, allowing for automated block detection to trigger the +deployment of new URLs, and for the :doc:`distribution lists ` to allow applications and end-users to discover +new URLs. + +Web Origins +----------- + +Static Origins +-------------- + +These have not yet been implemented. + +Simple Proxies +-------------- + +Smart Proxies +------------- + +Where a simple proxy leads to a broken user experience, it may be necessary to use a smart proxy to mitigate the +brokenness.