[cryptography] London Hum Used to Timestamp Recordings

mheyman at gmail.com mheyman at gmail.com
Fri Dec 14 08:56:29 EST 2012

>From <http://tech.slashdot.org/story/12/12/14/0229248/electrical-grid-hum-used-to-time-locate-any-digital-recording>

    "It appears that the Metropolitan Police in London have been recording the
    frequency of the mains supply for the past 7 years. With this,
they claim to
    be able to pick up the hum from any digital recording and tell when the
    recording was made. From the article: 'Comparing the unique pattern of the
    frequencies on an audio recording with a database that has been logging
    these changes for 24 hours a day, 365 days a year provides a digital
    watermark: a date and time stamp on the recording.'"

I hope they kept that recording secret. Anybody can start recording
now and then backdate things like recorded verbal agreements.
-Michael Heyman

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