Seal and Operation

Operation

In the Mitum blockchain network, an operation is a unit of command that changes data.

For example, Mitum Currency has operations of create-account, transfer, key-updater, currency-register, currency-policy-updater, and suffrage-infration.

Each operation requires a signature made with a private key according to its contents.

The fact in the operation contains the contents to be executed and the hash value summarizing the body of the fact.

Fact and token

Every operation contains a fact. In other words, the content of the operation is actually contained in the fact.

Facts play an important role in Mitum blockchain network.

The fact hash is a value representing the processed operation.
The fact hash must have a unique value in the blockchain.
So to check whether the operation is stored in the block, it can be retrieved using the fact hash.

In fact, the contents of the facts can be duplicated.

For example,

- The contents that `sender A sends 100 to receiver B` must always have the same fact.
- Fact hashes created using the same fact content can result in duplicate values.
- If there are two or more operations that result in duplicate values of the fact hash, only the first operation is processed and the remaining operations are ignored.

If so, does that mean that operations with the same fact content cannot be duplicated?

Don’t worry, in each fact, we use a value called token to make it unique.

The token is a value added to the essential contents of the operation.

The following json file is an example of fact.

{
    "_hint": "mitum-currency-create-accounts-operation-fact-v0.0.1",
    "hash": "3Zdg5ZVdNFRbwX5WU7Nada3Wnx5VEgkHrDLVLkE8FMs1",
    "token": "cmFpc2VkIGJ5",
    "sender": "8PdeEpvqfyL3uZFHRZG5PS3JngYUzFFUGPvCg29C2dBnmca",
    "items": [
        {
            "_hint": "mitum-currency-create-accounts-single-amount-v0.0.1",
            "keys": {
                "_hint": "mitum-currency-keys-v0.0.1",
                "keys": [
                    {
                        "_hint": "mitum-currency-key-v0.0.1",
                        "weight": 100,
                        "key": "2Aopgs1nSzNCWLvQx5fkBJCi2uxjYBfN8TqneqFd9DzGcmpu"
                    }
                ],
                "threshold": 100
            },
            "amounts": [
                {
                    "_hint": "mitum-currency-amount-v0.0.1",
                    "amount": "333",
                    "currency": "MCC"
                }
            ]
        }
    ]
}

The role of the token resembles that of a memo, but is capable of making a fact unique by giving different token values for the same fact content.

Making the fact that is essential for every operation unique expands usability in several ways.

The biggest advantage is that you can simply check whether the operation is processed or not as you exactly know the contents of the fact along with the token.
In the example above, anyone can calculate the fact hash if they know: the sender, receiver, currencyID, amount of currency, and a specific token value used.
Therefore, anyone can inquire whether the corresponding operation has been processed with the fact hash.

A fact hash is like a public proof recorded in a blockchain. There can be various applications depending on how a user uses the evidence disclosed in the blockchain.

For example, even an outsider who does not have a direct account in the blockchain can check the fact hash, the only value indicating whether the operation is processed or not, and make the implementation based on that.

In addition, facts and tokens can practically be used in models that deal with various data including remittance.

Seal

Seal is a collection of operations transmitted to the network. In other words, the operation is contained in the seal and transmitted.

To transmit the seal, a signature made with a private key is required.
To create signature, you must use the private key created in Mitum’s keypair package.
Seal can contain up to 100 operations.

The private key used for the signature has nothing to do with the blockchain account. In other words, it doesn’t have to be the private key used by the account.

Send

After creating an operation, the client creates and attaches a signature.

Create as many operations as necessary within the maximum number able to be included in the seal, and put them in the seal.
Create and put a signature on the seal.
Send seal to Mitum node.

Stored in Block

The operation transmitted to the Blockchain network changes the state of the account if it is normal and is finally saved in the block.

Whether the operation is confirmed and saved in the block can be checked through rest api.