L2Cap PSM Service UUID, PSM UUID vs BLE Service UUID, Characteristic UUID

App & System Services General
Zaid OP
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This post is from the Activity Core Bluetooth Q&A.

Is the PSM UUID format is less stringent than the BLE Service and Characteristic UUID? In our BLE cluster we broadcast both for different tasks... is a GATT and L2Cap mixed cluster of Apple devices ok?

Answered by Engineer in 892947022

Hello. I do not have a definitive answer here, this is something you will need to investigate and research for your specific use case, based on the latency requirements, throughput requirements, and the phones this is used on. You can also join the Security Q&A sessions or use other Apple security resources to help you understand the different recommendations, requirements and impact to your own use case.

Replies  7
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Views  352
Participants  2
Engineer OP
Apple

Hello. PSM is defined differently than a UUID, it is a 16 byte numeric value that is automatically assigned when you publish on an iOS device, its not a complete UUID which can be either 2 bytes or 16 bytes. Can you elaborate more on the mixed cluster of devices ?
Zaid OP

Our Apple device cluster implements a single iPhone central and many iPhone peripherals which share their content to the iPhone central to process.The central sends its results to specific or all Apple peripherals. It’s an initial reimplementation of Multipeer Connectivity... so initial discovery and auth is processed via GATT and then streaming content is processed via L2Cap.

Engineer OP
Apple

Ok, thanks for the clarification. That should still work - which device is publishing the PSM, which device is connecting to an existing PSM ? Are you publishing a single PSM or multiple ones on a single device?
Zaid OP

after authentication, the central publishes to the peripheral so the central can have a 1/2 dozen or so open streams but each peripheral will have 1 stream open to its central... that's the current use case until we implement full MPC with multi-peer streams

Engineer OP
Apple

Thanks for that info. One central can connect to multiple remote PSM's. Is there anything else I can help with ?
Zaid OP

I normally implement Apple-based algorithms for custom encryption in our wifi based MPC clusters and have opted to use the CoreBluetooth standard encryption for both Gatt and L2Cap connections. Any guidance in using public key and/or Apple's post-quantum encryption in the Bluetooth cluster or do you think that is too heavy? Much thanks

Engineer OP
Apple
Accepted Answer

Hello. I do not have a definitive answer here, this is something you will need to investigate and research for your specific use case, based on the latency requirements, throughput requirements, and the phones this is used on. You can also join the Security Q&A sessions or use other Apple security resources to help you understand the different recommendations, requirements and impact to your own use case.