Re: [Ace] EST over CoAP: Randomness
Michael StJohns <mstjohns@comcast.net> Sun, 19 May 2019 18:16 UTC
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From: Michael StJohns <mstjohns@comcast.net>
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Subject: Re: [Ace] EST over CoAP: Randomness
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On 5/14/2019 7:29 PM, Hannes Tschofenig wrote: > Hi Paul, > > My understanding from reading the draft text was that the "cost" was actually talking about "energy cost" rather than "monetary cost". > The monetary cost may also be interesting. > > It is difficult to judge the extra cost of a RNG in an MCU because > (a) you rarely find an MCU with and without MCU (keeping all other features the same), "with and without RNG"? > (b) even if you find one there are other factors that impact the cost (such as popularity of a particular MCU), > (c) RNG features are often provided with other features (such as SHA256 and AES in hardware), and Um... you usually need one or the other of these to do a good implementation of a DRBG and hardware versions tend to be less "costly" energy wise than software ones. > (d) cost and price of an MCU are different aspects. That have no bearing on the protocol design past a certain set of minimums. I'm beginning to think its time for "minimum requirements for internet hosts - 2020 edition" RFCs. We seem to be back in the same set of arguments that ANYTHING should be able to be an internet device albiet with even lower thresholds than we were a few years ago. ACE is pushing those boundaries, but we seem to be chasing "cost -> 0" > > Ciao > Hannes All good points, but ignoring the fact that needs drive the protocols which drive the MCU development. NOT MCUs limit the protocols which limit the needs. In other words, if the community (through protocol definitions) doesn't require the RNG, then the MCU developers won't include it. With respect to RNG energy costs - the argument that they are too expensive energy wise is pretty bogus. RNGs generally have two parts - a TRNG or entropy source, and a DRBG seeded from the entropy source. The energy costs for the DRBG are microscopic. The energy costs for a TRNG are related more to the time needed to initially fill the entropy pool (e.g. getting the noisy diodes making noise, getting the ring oscillators ringing etc) than to keeping it running to get a few thousand bits. Doing this say once a year to seed the DRBG isn't going to kill the lifetime of a battery device.
- [Ace] EST over CoAP: Randomness Hannes Tschofenig
- Re: [Ace] EST over CoAP: Randomness Eliot Lear
- Re: [Ace] EST over CoAP: Randomness Panos Kampanakis (pkampana)
- Re: [Ace] EST over CoAP: Randomness Hannes Tschofenig
- Re: [Ace] EST over CoAP: Randomness Panos Kampanakis (pkampana)
- Re: [Ace] EST over CoAP: Randomness Esko Dijk
- Re: [Ace] EST over CoAP: Randomness Hannes Tschofenig
- Re: [Ace] EST over CoAP: Randomness Hannes Tschofenig
- Re: [Ace] EST over CoAP: Randomness Esko Dijk
- Re: [Ace] EST over CoAP: Randomness Hannes Tschofenig
- Re: [Ace] EST over CoAP: Randomness Paul Duffy
- Re: [Ace] EST over CoAP: Randomness Hannes Tschofenig
- Re: [Ace] EST over CoAP: Randomness Michael Richardson
- Re: [Ace] [EXTERNAL] Re: EST over CoAP: Randomness Damm, Benjamin
- Re: [Ace] EST over CoAP: Randomness Paul Duffy
- Re: [Ace] [EXTERNAL] Re: EST over CoAP: Randomness Panos Kampanakis (pkampana)
- Re: [Ace] EST over CoAP: Randomness Panos Kampanakis (pkampana)
- Re: [Ace] EST over CoAP: Randomness Michael StJohns
- Re: [Ace] EST over CoAP: Randomness Hannes Tschofenig