(or NETSUKE)
Net’s Key is a tiny hardware, you can have on your side, pocket or wherever you want 
Storage Function
- little storage (as a USB key…)
Communication Function
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connectivity with other devices. I suggest a mini-jack, for any smartphone including Iphones (inspired by system of smartphone-payment, like Squareup). Could be useful for transaction in real-life with Safecoin… And mini-hdmi, for screens in particular… Could be useful for a Google Chromecast’s like usage.
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connectivity with other Net’s Key via Bluetooth, UWB or Zigbee. Could be useful for secured wireless communication mesh networks designed in the way of the Open Garden network)
Security Function
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access checked by sensors (for initiating PoH, or just like a kind of signature for using a particular Net’s Key (PoH could/must have other rules), with various possibilities of implementation… finger vein, heart beat or others). A stolen Net’s Key can’t be used without passing the security.
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trust levels software, for PoH also, or just for limitation/tribe communication : you could choose to communicate what you want with who you want depending of trust levels configuration. For example, if you think sensors are not efficient for PoH, you could check by your own if a user is a true human by meeting him physically and exchanging a “visit card”. It’s a kind of ranking system, not community oriented with a public hierarchy, but self-user oriented with a private/anonymous hierarchy.
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“visit card” is an authentication crypto-key between only two Net’s Keys you can construct by pairing Net’s Keys in a process you have to connect them “physically” (could be wireless with a range of 10 meters, may be…). It’s a configuration process in which you define a communication model between two Net’s Keys from “nothing” (just for PoH), to a certain type of data, only a particular movie (if you want to broadcast a movie from your personal stored data to a screen in a public area), for one hour or a year (could be useful for contracts between companies and employees), or whatever parameters you want.
Inspired by the japanese typical visit card exchanging process 
Default softwares Function
- SAFE Network Plug’n Play package : no download or complex installation, you just have to plug your Net’s Key on any device and it can run on the SAFE Network… (with an app for search on a SAFE Appstore, a SAFE-browser and other apps for minimal configuration)
I’m not sure the better is an “only one Net’s Key by person” policy, or a few… (up to ?).
I understand this “side project” is quite ambitious…
But I think it might solve some problems of some threads yet discussed, contribute to a SAFE Network popular/common use, and offer a lot of other opportunities/possibilities in different fields.
Does this “Net’s Key” project make any sense for you ?
Ps. Sorry for my french accent and poor english…
Ps 2. It’s my first post, I’m a newbee dev, but I just want to contribute with all my energies 
Yoroshiku !