Newly implemented GCM encryption method #442
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zerzhang
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Pull request overview
Implements support for SwitchBot’s upcoming AES-GCM encryption mode (alongside existing AES-CTR) for encrypted BLE devices.
Changes:
- Added
AESModedetection from the encryption init response and mode-specific IV parsing (CTR=16 bytes, GCM=12 bytes with padding trim). - Updated encryption/decryption flow to support GCM (including returning a 2-byte header derived from the GCM tag and incrementing GCM IV after encrypted commands).
- Expanded unit tests to cover mode resolution, GCM IV increment behavior, and updated
_encryptreturn shape.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
switchbot/devices/device.py |
Adds AES mode enum/detection, GCM-specific IV parsing, encryption/decryption changes, and GCM IV increment logic. |
tests/test_encrypted_device.py |
Updates tests for new _encrypt return type and adds coverage for GCM mode behavior and mode resolution. |
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bdraco
approved these changes
Jan 25, 2026
Member
|
Thanks @zerzhang I did some tweaks. If its all still working as expected, please let me know and I'll merge and do a release. |
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Author
@bdraco All works well |
fankai777
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to fankai777/pySwitchbot
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Jan 26, 2026
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: J. Nick Koston <nick@koston.org> Co-authored-by: J. Nick Koston <nick@home-assistant.io>
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Breaking change
SwitchBot will be implementing the new AES_GCM encryption method in its upcoming firmware update.
Switchbot Encryption Modes (CTR/GCM)
Mode Identification
2) indicates the encryption mode:0x00: AES-CTR0x01: AES-GCM0x00/0x01will throw an exception.IV Parsing
result[4:]from the random number response, length is 16 bytes.result[4:-4]from the random number response, length is 12 bytes (the last 4 bytes are for compatibility padding).GCM IV Increment Rule
GCM Tag Handling
decryptor.update(...), notfinalize().