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The KWR-37 "JASON" was the receiver part of the KW-37 crypto system, developed by the NSA In the 1950's. The systems consisted of a KWT-37 transmitter and a KWR-37 receiver. It was used to secure fleet broadcasts of the US Navy. The shore station transmitted 24 hours a day a continuous stream of encrypted random data. If a message had to be sent to one of the ships, the encrypted message was inserted into the continuous stream. An enemy eavesdropper could not detect if or how many message were sent, when they started or ended, or how long they were. Therefore, the KW-37 system made traffic analysis by the adversary impossible. The output of the receiver was connected to a teletype machine that immediately printed the decrypted stream onto paper. Transmitter and receiver maintained synchronisation whole day. If synchronisation was lost, the receiving operator could re-established synchro by re-setting and running very fast through all past key stream until the KWR-37 could pick up the current stream again.
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