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123 lines
4.8 KiB
Markdown
123 lines
4.8 KiB
Markdown
*worked on this a few days offtime, now here is the first working source*
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# esp-ena
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Implementation of the Covid-19 Exposure Notification API by Apple and Google on an ESP32 (with ESP-IDF).
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More information about the Covid-19 Exposure Notification at [Apple](https://www.apple.com/covid19/contacttracing/) and [Google](https://www.google.com/covid19/exposurenotifications/). This is meant for people without smartphone or without smartphones with Apples/Googles implementation.
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This implementation covers for now the BLE part including the cryptography specifications needed (see Bluetooth Specifications and Cryptography Specifications documents in the links above):
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* send tokens
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* store send tokens on flash (last 14 tokens)
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* receive tokens
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* received tokens are stored after 5 minutes threshold (storage is limited, ~100k tokens can be stored)
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Features missing for now are:
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* compare received tokens with infected list
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* calculating risks scores
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Extensions planned:
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* add RTC (will test DS3231)
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* add display (will test SSD1306)
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* interface to
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* set time
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* delete tokens
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* show status
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* report infection?
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* receive infected token list for Germany (will test [Corona Warn App](https://github.com/corona-warn-app))
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* send infected status (will test [Corona Warn App](https://github.com/corona-warn-app))
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* battery support
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* 3d print case
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Limitations/Problems
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* storage only ~2.8mb available
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* WiFi or other external connection needed for infections status (auto-connect to open WiFis?)
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* obtaining accessibility
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* all parameters (scanning time, thresholds etc.)
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The following acronyms will be used in code and comments:
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* *ENA* Exposure Notification Api
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* *ENIN* ENIntervalNumber - timestamp with 10 minutes resolution
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* *TEK* Temporary Exposure Key - personal secret key changed every 24h, published when infected
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* *RPI* Rolling Proximity Identifier - send and received identifer changed every 10 minutes
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* *AEM* Associated Encrypted Metadata - send and received metadata
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Open questions
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* now save ENIN for stored detection (documentation says timestamp), but for infection status ENIN should be enough!?
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* service UUID is send reversed, must RPI and AEM also beeing send in reverse? Don't know BLE specification enough
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* fixed change of advertise payload every 10 minutes, random value between ~15 minutes better?
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## How to use
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### Hardware Required
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For now just an ESP32 is required. For full device later RTC (DS3231) and Display (SSD1306) will be required.
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### Configure the project
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```
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idf.py menuconfig
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```
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required
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* enable bluetooth (BLE)
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* add partition-table for storage (currently hardcoded name "ena")
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* mbedTLS enable HKDF
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recommended
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* BLE Scan Duplicate (By Device Address and Advertising Data)
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### Build and Flash
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Build the project and flash it to the board, then run monitor tool to view serial output:
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```
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idf.py -p PORT flash monitor
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```
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(Replace PORT with the name of the serial port to use.)
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(To exit the serial monitor, type ``Ctrl-]``.)
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## Example Output
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For now some debug outputs are set. Besides, after each scan a CSV output is printed with stored TEKs, temporary detections (RPI) and full detections (RPI)
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```
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I (1201484) ESP-ENA-advertise: payload for ENIN 2657432
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D (1201494) ESP-ENA-advertise: 0x3ffbb6c4 02 01 1a 03 03 6f fd 17 16 6f fd 9a ee 95 9a 24 |.....o...o.....$|
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D (1201494) ESP-ENA-advertise: 0x3ffbb6d4 f0 f9 8e 56 0f 6d 68 5f ac 12 e5 7f 94 a1 47 |...V.mh_......G|
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I (1201524) ESP-ENA-scan: start scanning...
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D (1202224) ESP-ENA-detection: New temporary detection at 0 with timestamp 1594459201
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D (1202224) ESP-ENA-detection: 19 05 e3 3a 73 16 4e 74 2d 48 fc 0c 41 f6 26 3b
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D (1202234) ESP-ENA-detection: 5e 7d a9 48
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D (1202234) ESP-ENA-detection: RSSI -79
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#,enin,tek
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0,2657430,d5 13 92 b2 44 e4 7e b6 ca a7 20 c4 f 37 c0 1c
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#,timestamp,rpi,aem,rssi
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0,1594459201,19 5 e3 3a 73 16 4e 74 2d 48 fc c 41 f6 26 3b,5e 7d a9 48,-79
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#,enin,rpi,aem,rssi
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0,2657430,c7 2e b6 66 af 84 42 db b d1 a 0 f1 fd 86 2,4d 1 b2 d1,-76
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1,2657431,19 5 e3 3a 73 16 4e 74 2d 48 fc c 41 f6 26 3b,5e 7d a9 48,-76
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I (1231754) ESP-ENA-scan: finished scanning...
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```
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## Troubleshooting
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Sometimes I get errors from BT-stack of ESP-IDF printed. Didn't affect functionality for now, but I also could not find out what it caused and what it means.
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```
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E (909164) BT_HCI: btu_hcif_hdl_command_complete opcode 0x2005 status 0xc
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```
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## Structure
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The project is divided in different files
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* *ena-crypto* covers cryptography part (key creation, encryption etc.)
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* *ena-storage* storage part to store own TEKs and detections
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* *ena-detection* handles scanned data by storing temporary detections, check for threshold and store full detections
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* *ena-bluetooth-scan* BLE scans for detecting other tokens
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* *ena-bluetooth-advertise* BLE advertising to send own tokens
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* *ena* run all together and timing for scanning and advertising
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* *main* start and run main program
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