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A new research system uses lasers to encrypt messages. A mirror reinjects part of the sending laser´s initial signal back into the device´s internal cavity, generating a new signal that chaotically fluctuates in amplitude. A modulator or coupler then injects a message into the new stream, which is all but unreadable if intercepted. The sending laser also transmits part of its initial signal into the intended receiving laser, allowing the latter to generate the identical chaotic signals. When the receiver gets the incoming stream, it filters out the chaotic signal, yielding the original message