Aggregate Transaction

Aggregated Transactions merge multiple transactions into one, allowing trustless swaps, and other advanced logic. NEM does this by generating a one-time disposable smart contract.

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Example of an aggregate transaction between two participants

When all involved accounts have cosigned the aggregate transaction, all the inner transactions are executed at the same time.

Aggregate complete

An aggregate transaction is complete when all the required participants have signed it.

The cosigners can sign the transaction without using the blockchain. Once it has all the required signatures, one of them can announce it to the network. If the inner transaction setup is valid, and there is no validation error, the transactions will get executed at the same time.

Aggregate complete transactions enable adding more transactions per block by gathering multiple inner transactions.

Aggregate bonded

An aggregate transaction is bonded when it requires signatures from other participants.

Note

Before announcing an aggregate bonded transaction, an account must announce and get confirmed a hash lock transaction locking 10 cat.currency.

Once an aggregate bonded is announced, it reaches partial state and notifies its status through WebSockets or HTTP API calls.

Every time a cosignatory signs the transaction and announces an aggregate bonded cosignature, the network checks if all the required cosigners have signed. When all signatures are acquired, the transaction changes to unconfirmed state until the network includes it in a block.

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Aggregate bonded transaction cycle

Examples

Sending payouts

Dan announces an aggregate transaction that merges two transfer transactions.

As Dan is the only required signatory, the transaction is considered complete after he signed. After announcing it to the network, Alice and Bob will receive the mosaics at the same time.

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Sending payouts with aggregate complete transactions

Multi-Asset Escrowed Transactions

In this example, Alice is buying tickets with currency.euro mosaic. When the ticket distributor cosigns the aggregate transaction, the swap will happen atomically.

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Multi-Asset Escrowed Transactions

Paying for others fees

Alice sends 10 currency.euro to Bob using an app to make payments. But Alice doesn’t own cat.currency to pay the transaction fee.

By creating an aggregate bonded transaction, Alice can convert EUR to cat.currency to pay the fee. Now, Alice and Bob can use NEM blockchain without ever having to buy or hold cat.currency.

Since the app creator can put their own branding on the open source payment app, Alice and Bob may not even know they are using blockchain.

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Paying for others fees

Guides

Schemas

Note

Configuration parameters are editable. Public network configuration may differ.

AggregateTransaction

Announce an aggregate transaction to combine multiple transactions together.

Version: 0x01

Entity type: 0x4141 (complete), 0x4241 (bonded)

Inlines:

Transaction

Property Type Description
payloadSize uint32 Transaction payload size in bytes. In other words, the total number of bytes occupied by all inner transactions.
transactions array(Transaction, size=payloadSize) Array of inner transactions. An aggregate transaction can contain up to 1000 inner transactions involving up to 15 different cosignatories. Other aggregate transactions are not allowed as inner transactions.
cosignatures array(Cosignature, __FILL__) Array of transaction cosignatures. Fills the remaining body space after transactions.

DetachedCosignature

Cosignature transactions are used to sign announced aggregate bonded transactions with missing cosignatures.

Inlines:

Property Type Description
parentHash Hash256 Aggregate bonded transaction hash to cosign.

Cosignature

Property Type Description
signer Key Cosigner public key.
signature Signature Transaction signature.

HashLockTransaction

Alias: LockFundsTransaction

Lock funds with a hash lock transaction before sending an aggregate bonded transaction. This transaction prevents spamming the partial cache with transactions that never will complete.

After enough funds are locked, the aggregate transaction can be announced and added into the partial transactions cache.

Note

It’s not necessary to sign the aggregate and its hash lock transaction with the same account. For example, if Bob wants to announce an aggregate and does not have enough funds to announce a hash lock transaction, he can ask Alice to send the hash lock funds transaction sharing the signed aggregate transaction hash.

Upon completion of the aggregate, the locked funds become available in the account that signed the initial hash lock transaction.

If the aggregate bonded transaction duration is reached without being signed by all cosignatories, the locked amount becomes a reward collected by the block harvester at the height where the lock expires.

Version: 0x01

Entity type: 0x4148

Inlines:

Property Type Description
mosaic UnresolvedMosaic Locked mosaic, must be at least 10 cat.currency.
duration BlockDuration Lock duration. Duration is allowed to lie up to 2 days.
hash Hash256 Aggregate bonded transaction hash that has to be confirmed before unlocking the mosaics.