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+# Belarus 2020--2021
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+
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+This repo contains data analysis related to the [Tor blocking events in
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+Belarus from
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+2020-2021](https://gitlab.torproject.org/tpo/anti-censorship/censorship-analysis/-/blob/main/reports/2020/belarus/2020-belarus-report.md).
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+In particular, in late February 2021, the censor apparently enumerated
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+the set of obfs4 bridges that were distributed via email and blocked
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+those bridges. Given the set of 1890 bridges that were distributed in
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+February 2021 prior to the 22nd and the subset of 93 email-distributed
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+obfs4 bridges, our goal was to detect based on low connection counts
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+from Belarus that the 93 email-distributed obfs4 bridges were blocked,
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+while avoiding false detections that the other bridges were blocked.
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+
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+Our main finding is that the 93 email-distributed obfs4 bridges that
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+were blocked were not commonly used in Belarus prior to the censorship
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+event. Very low connection counts (e.g., 0) were common, so we were
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+unable to infer censorship of these bridges based on this signal.
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+
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+## Reproducing our results
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+
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+Dependencies:
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+- bash
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+- curl
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+- python3
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+- numpy
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+
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+To reproduce our results, just run `./run.sh`. **This will take a long
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+time (about 12.5 hours on my device) and require a few GB of free
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+space.** The reason is that it needs to download all extra-info records
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+for all bridges from 2020-07 to 2021-04 from the Tor Project's CollecTor
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+service (734 MB compressed, about 20 GB uncompressed), extract that
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+data, and obtain the needed information (bridge fingerprint, record
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+date, and connection count from Belarus) from each record. There are A
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+LOT of these records.
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+
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+If you want to avoid spending all the time to do that, you can run
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+`./run.sh --fast`, which starts with a 6.7 MB archive (87 MB
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+uncompressed) containing only the information we need.
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+
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+## Julian dates
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+
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+Note: The Julian date conversion in get-bridge-data.sh and get-stats.py
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+is 1 day earlier than reported by, e.g.,
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+https://aa.usno.navy.mil/data/JulianDate. What matters is that these two
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+files use the *same representation* of a date, which they do.
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