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Document: draft-ietf-lwig-crypto-sensors-05
Reviewer: Dan Romascanu
Review Date: 2018-02-13
IETF LC End Date: 2018-02-19
IESG Telechat date: 2018-02-22

Summary:

This is a well-written clear informational memo, documenting methods to secure networks built of resource-constrained devices. It describes a deployment model based on exchanges of signed objects, and documents available cryptographic libraries that may be suited to the targets. The conclusions include analysis of trade-offs and recommendations for future development and deployments. 

The document is READY from Gen-ART perspective. There are a couple of non-blocking issues that I would be glad to have them clarified before approval. I have also pointed to a couple of nits. 

Major issues:

Minor issues:

1. In Section 7: 

'The location of the resource directory was configured into
   the smart object sensor by hardcoding the IP address'

Is this reasonable? I understand that the goal of the exercise was to demonstrate that it is possible to implement the entire architecture with public-key cryptography on an 8-bit micro-controller, but hard-coding the IP address seems to be below the threshold of a functional system. IMO there is a need to be able for the sensor to acquire this address (DHCP stack, or a simple UI to stream in one address, etc.)

2. In section 8.1 - I would expect some discussion about the extra-power needed to run the cryptography. There is a statement about these being less than device wake-up and sending messages, but some quantitative evaluation (in percentage) of the impact would be useful, taking into account that battery capacity is one of the most important constrained resources. 


Nits/editorial comments: 

1. The document uses the alternate term of 'small devices' for 'resource-constraint devices'. I view this as kind of an inaccurate verbal automatism in the world of IoT, as 'small' is a relative term, resource-constrained devices are not necessarily small (like in reduced physical footprint), and small devices can be rich in resources. I would suggest to either avoid the term, or explain what it means in the context (e.g. ''Smart objects', 'small devices' and 'resource-constrained devices are used interchangeably in this document and mean ...') 

2. Please expand ECDSA at first occurrence