Editing Secure communication (section)

== Nature and limits of security ==

=== Types of security ===
Security can be broadly categorized under the following headings, with examples:

* Hiding the content or nature of a communication
** [[Code]] – a rule to convert a piece of information (for example, a letter, word, phrase, or gesture) into another form or representation (one sign into another sign), not necessarily of the same type. In communications and information processing, encoding is the process by which information from a source is converted into symbols to be communicated. Decoding is the reverse process, converting these code symbols back into information understandable by a receiver. One reason for coding is to enable communication in places where ordinary spoken or written language is difficult or impossible. For example, semaphore, where the configuration of flags held by a signaler or the arms of a [[Semaphore line|semaphore tower]] encodes parts of the message, typically individual letters and numbers. Another person standing a great distance away can interpret the flags and reproduce the words sent.
** [[Obfuscation]]
** [[Encryption]]
** [[Steganography]]
** [[Identity-based security|Identity Based]]
* Hiding the parties to a communication – preventing identification, promoting [[anonymity]]
** "[[Crowds (anonymity network)|Crowds]]" and similar anonymous group structures – it is difficult to identify who said what when it comes from a "crowd"
** Anonymous communication devices – [[Prepaid mobile phone#Privacy rights|unregistered cellphones]], [[Internet cafe]]s
** [[Anonymous proxies]]
** Hard-to-trace [[routing]] methods – through unauthorized third-party systems, or relays
* Hiding the fact that a communication takes place
** "Security by obscurity" – similar to needle in a haystack
** Random traffic – creating random data flow to make the presence of genuine communication harder to detect and [[traffic analysis]] less reliable

Each of the three types of security is important, and depending on the circumstances, any of these may be critical. For example, if a communication is not readily identifiable, then it is unlikely to attract attention for identification of parties, and the mere fact a communication has taken place (regardless of content) is often enough by itself to establish an evidential link in legal prosecutions. It is also important with computers, to be sure where the security is applied, and what is covered.