Comment by miki123211

You couldn't do this with current chips I don't think, but if you had at least 256 bytes of randomness on the chip, you could.

The simplest way to do this would be to use the random data for an EC25519 private key, which would be used to encrypt the data[1] and then sign the encrypted blob plus an unencrypted timestamp. The registry would be a mapping of public keys to encrypted records. Updates could be accomplished by sending a record with a greater timestamp, which would then be propagated to other nodes.

You could also put a DHT on top of that to minimize storage requirements, perhaps also a PoW scheme for sibil resistance.

[1] EC doesn't technically do encryption, but that can be worked around by attaching a public key for an ephemeral keypair for your message, doing a DH against the two keypairs, and using the resulting secret as a key for symmetric encryption.