To help you we should understand completely in order to be able to share correct and right advice or information, it seems we need to know more detail of the concept of your project. I think you will do some comparative to other existing crypto to find unique solution.   

Hello
Greetings!!!

I just read your post and according to my understanding, you are looking for a data (Message) transfer at the time of transaction means you want to make a functionality like while transferring crypto you need to provide a message box to write the reason for the transaction.

Please correct me if I am wrong.

Rest, please let me know your good time to schedule a quick call to discuss about the requirements properly.

Hope to hear from you soon with a positive response.
Thanks and Regards,
Arun Sachdeva
Telegram: @arunsachdeva
LinkedIn: https://www.linkedin.com/in/arunsachdeva/
Email: arun@revinfotech.com
Skype: mvteams1

Hi, just some proofreading (well, not from native speaker though): I think "suply chain data" should be changed to "supply chain data" on the main diagram.

There is no reason for the number '6', its only a number of confirmation adopted by most of the services, because when you have more confirmations, more difficult to the miners reverse the transaction. In truth its very difficult to happen, the attacker needs a big percentage of the total hash rate to reverse the transaction even after only one or two cofirmations, and try to mine again a block to try to build a new longest chain above the old block is not profitable since you are competing with other miners which are already mining the longest chain.

You can calcule the probability for a miner to reverse a transaction here: people.xiph.org/~greg/attack_success.html

It doesn't need 6 confirmations to be finalized.
Bust many exchanges and websites will wait for 6 confirmations before accepting it, as a transaction is only considered irreversible with 6 confirmations.

ae ai chưa biết powtoken thì tranh thủ tham gia kiếm vài $ nhé , cái này giống hồi đợt stellar
ref ủng hộ e nhé 
http://www.powtoken.com?ref=pow2921

The price not reach $0 you know why guys? It is because there were lost wallet out there that really cost too much and with lots of btc on it. And there lots more lost coin out there, so there will be no reason to turn this thousands of dollars into zero balance. And also people will not let bitcoin fail, so.exchange will never be worry about that because big investors will really hold their coins for long, How I wish I can be one of them, rich man with btc in my wallet. So I will.not let btc value fall so down.

Only YOU need to save your private and public key (private key is enough, because the public key can be created out of the private key if you lose your public key).

Nobody else need to know which public or private keys exists or were used.

Some basics:
Private/public key pairs have the following attributes

• A private key can be created randomly
• You can create the public key out of the private key with some mathematical rules
• You CANNOT create the private key out of the public key -> so you can safely pass the public key (in Bitcoin it's actually a hash of the public key) to anyone without risking they can create the private key out if this public key
• You can sign a message (in Bitcoin the message is a transaction) with your private key
• You can prove with the public key, that a message was signed by the corresponding private key

With this in mind let's assume, you own 1 Bitcoin which was previously sent to one of your Public keys.
If you want to spent this 1 Bitcoin, you need to create a transaction.
Within this transaction you need to prove, that you own the private key of the public key which holds the 1 Bitcoin.
You can do this, by signing the transaction with your private key. As we learned above, when you sign something with your private key, anybody else can check with the public key (which is also included in the transaction), that the signature was created by your private key.
In the transaction you also pass a recipients public key where you want to send the Bitcoin.

This transaction is passed to the Bitcoin network (send the transaction to each Bitcoin node which is connected to your Bitcoin node (Wallet)). Each node will verify if this transaction is valid. One check to verify is, if your created signature matches with the public key which holds the Bitcoin. If you sign with a wrong private key, the transaction is invalid and will not be forwarded to the next  Bitcoin node. If it is valid, it will be forwarded to all other nodes in the Bitcoin network.
After some time, a miner will take your transaction and put it in one block he mined.

This shows, that it is not needed to track which public keys were already used.
You just prove that you are the owner of the private key by signing the transaction.

No.