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A comment on NSA “precomputed contact chaining” enhances phone-record tracking program. Parent comment

Re:NSA “precomputed contact chaining” enhances phone-record ... by walterbell on Sunday May 24, 2020 @02:59PM (#23293742)
It can be used to derive phone/human proximity data, which can be cross-referenced with other metadata.
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Re:NSA “precomputed contact chaining” enhances phone-record ... by conradev on Sunday May 24, 2020 @03:39PM (#23294067)
It can’t be because the database does not exist: it is sharded onto each individual phone

The server only has a list of random identifiers from those who have tested positive for COVID. An exposure notification is determined when a phone downloads that list and correlates it with its local list.

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Re:NSA “precomputed contact chaining” enhances phone-record ... by walterbell on Sunday May 24, 2020 @03:51PM (#23294171)
> when a phone downloads that list

After exposure, a time-bounded (?) graph of proximity contact data can join the central list, via the state health app using the local data. This can be cross-referenced with other metadata.

Once a human contact tracer establishes communication with the owner of a phone's random identifier, the identifier can be de-anonymized.

Even without the new APIs, each phone's location can be collected and shared by telcos, at the granularity of cell tower triangulation.

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