The smallest size alphabet you can use is two (0.1) and the largest what ever size alphabet you find convenient.įor historical reasons to do with charging “per word” in “cables” back at the begining of the 20th Century what is now the “International Telegraph Union”(ITU an agency of the UN) set the “word size” at “five letters” to stop people using “codes” to reduce the amount they paid.
Which is a major difference in metadata.īut does this effect the crypto security, the answer is “probably not”, “it’s all down to the statiatics”. Thus all message metadata should look alike.īut in the case of the “nein nines” messages the alphabet instead of having ten symbols (0.9) it had only nine (0-8). Whilst these appear “random” the Indicators are often unique and the groups of fixed size, with an “alphabet” that has uniform usage properties and flat statistics. So traffic times number of messages sent even the message length sent etc etc is maintained without change for not just weeks or months but in some cases decades. With “broadcast systems” such as SW/HF Numbers stations the meta data is known by anybody who has a receiver tuned to the station and is in range of the transmitter.Īs Matt notes to make the meta-data of little use to anybody listening things are kept as near identical as can be with the metadata. So the fact a message was sent at what time of day, day of the week/month/year is often called “meta data” (data about data).
I mentioned it the other day over on one of the squid pages.Īs a slightly over generalised rule of thumb “Crypto only secures the message contents, not the traffic”. But their capture may have illustrated how subtle errors bcan cause these systems to fail badly in practice, even when the cryptography itself is sound.“ “numbers stations are part of time-honored espionage tradecraft for communicating with covert agents.
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