1

I have an open source offline airgapped encrypted device for signing transactions.
Seeds are stored on this device.

Signed transactions are passed to an online machine as a parade of qr-codes for broadcasting to the Tangle.

The online device holds the index, security level, and addresses, but not the seed.
This helps me:
1. Keep track of what addresses have already been used.
2. Look up balances.
3. Send out addresses in order to receive payments.

The online device is not secure because it connects to other devices and to the Internet. If an adversary gains access to this device, can the list of indexes, security levels and addresses be used to crack the seed? Common sense makes me think not but the question is worth asking because many people may wish to manage their funds this way.

Thanks for the clarification.

2

After thinking about this, I conclude that the only thing which needs to be protected is the seed. So I am free to store addresses, indexes, and security levels on an unsecured machine. I have already been advised that spending more than once from the same address exposes part of the seed. So no spending twice from the same address.

The only vulnerability I can think of right now is if an adversary changes one of my addresses on the unsecured machine to an address of their own. Then when I hand out that address for payment, my customer would be paying my adversary. So it will be best to keep track of all my addresses, indexes security levels, and balances using my offline machine and only use the online machine for broadcasting the signed bundle.

After thinking some more I realize that when handing out addresses for payments, these addresses should come from the secure offline device as a signed GPG message to prevent switching. humm - starting to think. IOTA does encrypted messaging. Going to look into that for sending addresses to customers.

  • I agree (except that double spending does not expose any part of the seed, but only a part of that address' private key - other addresses are safe). You can also consider that from a typical "Snapshot recovery" bundle created by Trinity wallet you can in most cases infer all indexes, addresses and security levels (=2) of all addresses used from that seed. If others make this information public, storing it on an insecure PC should not be harmful. – mihi Mar 21 at 21:39
  • Thank you for the clarification mihi. Hope to post a very simple offline wallet on github soon. – John Shearing Mar 22 at 5:07

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