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Nimiq PoS has four different account types, each with unique features and purposes. Each account has an individual address assigned, enabling users to interact with the blockchain.

  • Basic account
  • HTLC (Hashed Timelock Contract)
  • Vesting Contract
  • Staking Contract

Basic account

With a basic account, users can send and receive NIM and have a balance. The account is controlled with a private key unique to the user. This type of account is similar to a bank account with an address, a balance, and a key. When a user sends or receives NIM, the corresponding balance is updated accordingly. A basic account is created once any user sends NIM to an inexistent address.


A HTLC is a conditional payment implemented by a script in the blockchain. It's a smart contract that enables a party to transfer assets to another party without relying on a third one. The contract acts as the escrow party for both sender and recipient.

Data fieldDescription
balanceThe amount of NIM at any given time. It can differ from the total_amount since it’s possible to withdraw partial amounts at a time
senderThe sender’s address
recipientThe recipient’s address
hash_rootThe hash of the pre_image - secret key
hash_countThe number of times the pre_image is hashed so the recipient can withdraw the funds entirely. If the hash_count is 2, the recipient can withdraw the funds in 2 portions
timeoutThe time, in Unix time with millisecond precision, when the contract elapses. The timeout is determined once the contract is created. If the time elapses, the sender can withdraw the funds
total_amountThe initial amount decided in the contract creation

Anyone can create a HTLC whose structural values are static (determined by the contract owner) besides the balance, which changes every time NIM is withdrawn. Also, once the HTLC is created, no NIM can be added to the contract.

There are three different transactions to unlock the funds, and each one results in a new balance on the HTLC:

  1. Timeout resolve: After the timeout elapses, the sender can redeem the funds.
  2. Regular transfer: The recipient can withdraw the funds entirely or partially before the timeout elapses. Supposing that the hash_count is three, the contract owner can present a hash that was rehashed two times resulting in the hash_root and then withdraw two-thirds of the funds. The owner can also present the pre_image and withdraw the total_amount immediately.
  3. Early resolve: When both sender and recipient sign the transaction the funds can be withdrawn at any time.

Vesting contract

The vesting contract allows a user to lock funds for a period of time and unlock them in a predefined timetable. This contract locks the funds of a single user (the contract owner), and it can unlock the funds in predefined portions.

Data fieldDescription
balanceThe amount of NIM at any given time. Whenever the funds are spent, the balance changes
ownerThe owner's address. The contract owner has a corresponding key to sign and withdraw the funds
start_timeThe time, in Unix time with millisecond precision, when the vesting schedule starts, decided by the contract owner
time_stepThe step_amount unlocks at each time_step. If the owner decides to unlock the funds every 24 hours, the step_amount unlocks at every 24 hours
step_amountThe amount of NIM unlocked in every time_step
total_amountThe initial amount decided in the contract creation

These values are static, except for the balance, which changes as the funds are withdrawn. The values are decided in the creation of the contract.

The contract owner can interact with the contract whenever but can only withdraw the partial amount of NIM decided when the time_step unlocks. The balance is then updated. Note that unlocking the funds is a predefined action, and it happens at every step_amount. Yet withdrawing the funds is an owner’s action. Also, once the vesting contract is created, no NIM can be added to the contract.

Staking contract

The staking contract is a specific type of contract designed to track and manage functions regarding validators, stakers, and staking activities. For a detailed explanation about the staking contract, follow this link.