See also my other comments. The device is tillitis TKey. There is a True RNG (source of entropy) but not recommended, i.e. not cryptographically-secure. However, together with Blake2s (in firmware) or another hash-function, you can at least approximate a source of reasonably secure randomness. Needs to be part of the your user program (to be loaded onto TKey), so you can make this as complicated as you like. You can indeed use the input-data as entropy/seed-bytes and hash it with other data and entropy from TRNG.I haven't tested yet how fast the TRNG refreshes. Right now, I take 4 bytes (1 collection) of TRNG entropy to be hashed with a static byte-buffer.
The RNG would be used for (sk_device,pk_device). So 'identity' keypair for authn, 'device' (ephemeral) keypair for key-exchange.
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