Well, USDT is extremely easier to implemented because it's centerlized service. Otherwise, I don't think there is any drawback/weakness for this kind of project over USDT or TUSD.

SSN vs Master Node:

1. SSN is a decentralized p2p network, where everyone can easily join, while MN is widely considered to becoming more and more centralized due to the extremely high entry requirement.

2. SSN nodes can come and go as they will, while MN relies on the high availability of its nodes.

3. SSN using Kademlia DHT allows the network to scale to any level of adoptation, while MN works like a cloud service, where nodes have to keep track of each other avalaibility.

4. Every SSN operation is recorded on-chain, so everyone can re-evaluated and audit. That prevents any kind of history forging and provides the Proof of Bad Conduct for the network to punish the bad nodes. Meanwhile, MN is an offchain solution, where nothing is recorded onchain.

SSN's Input Locking vs MN's InstaSend:

1. SSN load balancing nature allow all transactions to be efficiently locked without any addition fee, while InstaSend only locks on request, with a higher fee.

2. SSN Input Locking mechanism relies on the collateralization and punishment, with 100% probability. That means, a locked transaction is either be finalized, or repaid by a bad node's collaterlized asset. Either ways, transaction receipients always get the value they are promised (by tx remitters and/or Input Locking Nodes).

Meanwhile, MN InstaSend only provides a high probability of finality. There's still chance that locked tx is double spent when 6/10 of selected nodes are compromised, and there's nothing MN can do about it.

Side Note: a prototype of SSN and Input Locking is being developed right now.

It is instant, you don't have to wait for new block to be mined. "Current block and previous block" means "lastest block and the one before it", I might need to clarify it in the paper. Thanks.

UTXO has to be signed by both current block and previous block set of nodes

By using the same request sampling process:
+ Input: ILS nodes list (from chain): S0-S1-...-S99, current block hash, input UTXO (block number & tx number)
+ Output: S1, S2 and S5

1. 2N+1 signatures are of: sender and 2N of ILS nodes.
2. All ILS node PubKeys can be calculated by everyone using the said Rejection Sampling (all data is on-chain).
3. As part of Schnorr Signature protocol, after the first handshake round with each ILS nodes, tx sender has the list of all available ILS nodes. He will create a bit mask (each bit for each ILS node), to mark all nodes with the signature. This bit mask (takes only 2N bit, or N/4 bytes) is included in the TX, and signed by the sender and all ILS nodes.
4. From the TX bit mask, everyone will know which ILS node signatures is aggregated in the Schnorr MultiSig. So they can verify the signature with all their PubKey aggregated.

Every participant need to verify the signature, including miners and SPV, and SSN nodes.

For example, the Input Locking Node can only be selected to lock an input, if its stake is no less than the input UTXO value.

A locked transaction with one input UTXO will contains up to 2N+1 signatures, and almost every transactions are locked using this service.

When you have an item list, with each item has a different chance to be selected, called frequency. You use Rejection Sampling or Frequency Counting to randomly pick one of them.

Frequency Counting is stacking up all the item, and count the total frequency. Pick a random number between 0 and total frequency. Start counting from the first item to pick the item located in that random number.

Rejection Sampling is to draw a frequency graph, and keep throwing dart to the board, until the dart hit the area bellow the graph.

4. Using Rejection Sampling or Frequency Counting algorithm on the list to select a
serving node.

Scott Steimle, [21.01.18 08:19]
[In reply to Pincoin Team]
tonight in what time zone?

성열 이, [21.01.18 08:39]
https://t.iost.io/?c=Nq4eEBSi

Colin Phillips, [21.01.18 11:16]
What is happening about the refunds?