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Callsigns and addresses are frequently encrypted , requiring assistance in identifying them. Traffic flow security[ edit ] Traffic-flow security is the use of measures that conceal the presence and properties of valid messages on a network to prevent traffic analysis.
This can be done by operational procedures or by the protection resulting from features inherent in some cryptographic equipment. This is also called masking or link encryption. Traffic-flow security is one aspect of communications security. Please help improve it or discuss these issues on the talk page. November 2011 This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed.
Non-content COMINT is usually used to deduce information about the user of a certain transmitter, such as locations, contacts, activity volume, routine and its exceptions. Examples[ edit ] For example, if a certain emitter is known as the radio transmitter of a certain unit, and by using direction finding DF tools, the position of the emitter is locatable; hence the changes of locations can be monitored.
Using all, or as much of the metadata available is commonly used to build up an Electronic Order of Battle EOB — mapping different entities in the battlefield and their connections. Of course the EOB could be built by tapping all the conversations and trying to understand which unit is where, but using the metadata with an automatic analysis tool enables a much faster and accurate EOB build-up that alongside tapping builds a much better and complete picture.
The German fleet sortied, and the British were late in meeting them at the Battle of Jutland. When the Germans crossed the frontier, the French worked out crude means for direction-finding based on intercepted signal intensity.
Recording of call-signs and volume of traffic further enabled them to identify German combat groups and to distinguish between fast-moving cavalry and slower infantry. Traffic analysis produced indications Scharnhorst and Gneisenau were moving into the North Sea, but the Admiralty dismissed the report as unproven.
The captain of Glorious did not keep sufficient lookout, and was subsequently surprised and sunk. Harry Hinsley , the young Bletchley Park liaison to the Admiralty, later said his reports from the traffic analysts were taken much more seriously thereafter. The ships, units, and commands involved were all in Japan and in touch by phone, courier, signal lamp, or even flag. None of that traffic was intercepted, and could not be analyzed.
At least one such vessel carried some Japanese Navy Intelligence officers. Such messages cannot be analyzed. It has been suggested,  however, the volume of diplomatic traffic to and from certain consular stations might have indicated places of interest to Japan, which might thus have suggested locations to concentrate traffic analysis and decryption efforts.
It is unclear if this deceived the U. The Japanese Navy played radio games to inhibit traffic analysis see Examples, below with the attack force after it sailed in late November. Radio operators normally assigned to carriers, with a characteristic Morse Code " fist ", transmitted from inland Japanese waters, suggesting the carriers were still near Japan Kahn  Operation Quicksilver , part of the British deception plan for the Invasion of Normandy in World War II , fed German intelligence a combination of true and false information about troop deployments in Britain, causing the Germans to deduce an order of battle which suggested an invasion at the Pas-de-Calais instead of Normandy.
The fictitious divisions created for this deception were supplied with real radio units, which maintained a flow of messages consistent with the deception. An attacker can gain important information by monitoring the frequency and timing of network packets. A timing attack on the SSH protocol can use timing information to deduce information about passwords since, during interactive session, SSH transmits each keystroke as a message.
Onion routing systems are used to gain anonymity. Traffic analysis can be used to attack anonymous communication systems like the Tor anonymity network. Murdoch and George Danezis from University of Cambridge presented  research showing that traffic-analysis allows adversaries to infer which nodes relay the anonymous streams. This reduces the anonymity provided by Tor.
They have shown that otherwise unrelated streams can be linked back to the same initiator. Remailer systems can also be attacked via traffic analysis. If a message is observed going to a remailing server, and an identical-length if now anonymized message is seen exiting the server soon after, a traffic analyst may be able to automatically connect the sender with the ultimate receiver. Variations of remailer operations exist that can make traffic analysis less effective.
Countermeasures[ edit ] It is difficult to defeat traffic analysis without both encrypting messages and masking the channel. When no actual messages are being sent, the channel can be masked  by sending dummy traffic, similar to the encrypted traffic, thereby keeping bandwidth usage constant.
The known solutions require Alice to send a continuous stream of messages at the maximum bandwidth she will ever use... This might be acceptable for military applications, but it is not for most civilian applications. The user cannot simply increase the bandwidth of the link, since masking would fill that as well. If masking, which often can be built into end-to-end encryptors, becomes common practice, ISPs will have to change their traffic assumptions.