Introduction

XELIS is not only a Smart Contracts platform, but can be also considered as a store of value and payments system. This means, XELIS has transaction capabilities on its network for transfering value.

To reward miners for their hard work keeping the blockchain a safe space and also preventing spamming attacks using high count of transactions, XELIS has a slightly different approach to calculate the required fee.

First, fees paid by a transaction can only be paid using XELIS (native) asset, and is based on more than one parameter. XELIS asset is used as a gas system, store of value and payments system.

Differents factors are used to calculate the required minimal fee per transaction.

This limit the advantages of using transactions as a vector of attack in case some dishonest people would try to harm the chain.

A fee system is necessary for security and to balance fees correctly between the need of low cost for users using the chain daily, but high enough to prevent bad actors from anormal usage.

Fee per KiB

The factor for this fee is based on the transaction size in raw bytes, we set a "storage fee" which is based on KiB (1 KiB = 1024 bytes). The lowest fee per KiB allowed by the protocol is set to 0.0001 XELIS (10 000 in atomic units).

This fee is used to prevent chain bloating and growing too fast in disk size.

It is dynamic because the protocol auto-regulate itself based on the current block usage to prevent bad actors to use our low fee model to attack the chain through congestion or forcing nodes to store a lot of data in a short time.

The dynamic base fee is calculated by a smooth EMA (Exponential Moving Average) on the block size.

For a simplified Python implementation and the graph generator for below images, see this (opens in a new tab) repo.

An exponential curve is generated to determine which base fee should be used based on the current chain usage.

Around ~50% of EMA block usage, the base fee is almost x4 compared to the minimum required. This can be explained by our short block time combined with our 1.25 MiB maximum block size which allows to pass a lot of transactions per second in case of high usage to reduce the congestion, but at the cost of a much higher price.

To reach >50% of EMA block usage, we would needs to support the daily transactions of Bitcoin, Ethereum and Monero combined.

Fee per Output

On XELIS, a transaction can make one or more output, requiring one or more ZK Proof and statement to execute it safely. This brings an additional cost that must be reflected on the fees paid by a user to miners.

The protocol charges an additional (static) fee of 0.00005 XELIS (5 000 in atomic units) per transaction output.

This is used to have an accurate fee based on the needed computation of Homomorphic Encryption ciphertexts and the verification of their ZK Proofs.

This basically means that, the more transfers you have in a transaction, the more it requires computation to be applied and verified. The extra fee only scale along the required computation to ensure fairness.

Fee per New Address

XELIS is based on the account model, which basically create an entry for said account and link all balances and transactions history to it.

To prevent any bad actors to bloat the chain with dummy accounts, an extra (static) fee is required for each newly generated account.

For each new address registered by a transaction, the transaction must pay an additional fee of 0.001 XELIS (100 000 in atomic units).

This is a one-time fee for each account that never had any record previously. It is not mandatory because an account can register itself by either mining a block or by already receiving a transaction.

Fee per Signature

In case your account is currently configured as a multisig wallet, you may see a slight overhead in fees paid compared to others accounts.

This is required by the protocol to scale correctly along the required computation on nodes and miners for verification.

Each additional signature present in a transaction require an additional fee of 0.00005 XELIS (5 000 in atomic units).

This extra fee is static and not subject to the chain usage.