Symbol Shared Node

Symbol’s ecosystem was developed by NEM foundation startup and became a more advanced version of NEM blockchain. The development was taking 4 years. Symbol was designed as the business-enterprise-facing project, for finances and supply chains. It is fast, secure, and scalable. The structure is complicated: it is built from a network of nodes and includes four levels. Symbol is quite a feature-rich platform. It has plugins and extensions (an analog of smart contracts), and the possibility of atomic swaps (cross-chain transactions). But the most interesting feature is the variety of transactions. The most special ones:

• 1. Aggregated transactions. It might be useful for any advanced logic, for example, trustless swaps. They could be processed by multiple signers: transactions are executed at the same time when all participants have cosigned.
• 2. Mosaics. It is a set of multiple identical things organized as a fixed asset. Mosaic could be a collection of assets such as bonus points, statuses, signatures, status flags, votes, and so on.
• 3. Transfers. Messaging between two Symbol accounts.

According to the documentation, there are 12 types of transactions in Symbol.

Basically, a transaction is a unit of work. In Symbol, it is an act signed by an account. An account is determined as a pair of keys (private + public key) stored on the blockchain. The process of signing is quite complex but due to this, the system is stable and secure. How transactions are signed in Symbol blockchain:

• 1. Get the bytes of the transaction except for the size, signature, and signer (so-called “signing bytes”);
• Get generation hash.
• 2. Add signing bytes to generation hash.
• 3. Add the nemesis block generation hash to the previous data.
• 4. Sign this string with the private key; the transaction signature will be received.
• 5. Add public key and the signature to get the payload
• 6. Get the transaction’s amount.

All the signed transactions go through two stages of validation; the last one is before building of the block. If it fails, the transactions are not considered complete and can be canceled. In Symbol, all the transactions have a time limit and a maximum fee. A time window is 2 hours by default but it could be up to 48 hours (depends on the transaction’s type). Max fee. The sender decides how much he can pay for the transaction to get it accepted. Completed transactions are recorded on the blockchain and can no longer be changed.

The network’s architecture is complicated: it is built from a network of nodes, with complex connections between them. The basic element of Symbol blockchain is the peer node. If one node fails, the Symbol blockchain will remain stable. Nodes verify transactions and blocks, create new blocks, spread data through the network, and keep the consensus algorithm working. Symbol is a Proof-of-Stake+ public blockchain. PoS+ algorithm is similar to regular Proof-of-Stake, but holders also have a rate of “importance”. There are three important factors: stake, transactions, and node availability. Nodes in the Symbol network also have a reputation rate. Because some nodes could share invalid information on purpose, all the nodes keep information about previous communication. Each node has a weight. The higher the weight, the more likely the node will be selected to read data.

Harvesting is the process of new block creation. There are three types of harvesting: Local, Remote, and Delegated. The last one is available for accounts that do not have their own nodes.

• 1. Local harvesting: to complete it, you need to fill in the appropriate section in the node configuration file. This method is unsafe due to the peculiarities of using the secret key which is stored in the harvester Signing Private Key, and therefore it can be compromised and used to steal funds.
• 2. Remote harvesting: the host is used as a proxy. This method is safe and recommended as there are no funds on remote recording.
• 3. Delegated harvesting: account can request a node to harvest for them

An account's participation in harvesting is determined by an importance rating. The rewards for generation are tokens and transaction fees.