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Frequently asked questions

Here you will find the most frequently asked questions about RSK, its vision, technology and other aspects

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What consensus protocol does RSK use?

The RSK blockchain is secured a variant of Nakamoto Consensus (PoW) called DECOR+. The proof-of-work is based on the SHA256D mining algorithm (the same algorithm that Bitcoin uses) and merge-mining is enabled. Merge-mining is a protocol that allows miners to mine on both RSK and the Bitcoin blockchains at the same time with exactly the same hardware miners and with no performance penalty. Therefore merge-miners can collect fees on both platforms. RSK has improved several open-source mining-pool softwares to enable merge-mining.

What is the DECOR+ protocol?

In the Bitcoin network, when two or more miners have solved blocks at equal height, there is a conflict of interests. Each competing miner wants his block to be selected by the remaining miners as the best-chain tip. All the remaining honest miners and users would prefer that everyone chooses the same block tip, because this reduces the block reversal probability. DECOR+ sets the right economic incentives for a convergent choice, without requiring further interaction between miners. The conflict is resolved so that:

  1. The resolution is agreed by all parties (consensus) when all parties have access to the same blockchain state information within a time bound (synchronous).
  2. If the system behaves partially synchronous, the conflict is resolved as in Nakamoto Consensus.
  3. The resolution maximizes all miners revenue when the conflicting block revenue (fees) is much higher than the average.
  4. The resolution reduces the power of the miners to censor other blocks or transactions when the conflicting block has a reward close to the average.
  5. Resolving the conflict takes negligible time.
Is RSK secure from selfish mining?

DECOR+, plus the “sticky” rule, is incentive-compatible (that miners gain nothing from withholding blocks) as long as the transaction fees are close to the average, and without miner payment side-channels. This last restriction means that the incentive-compatible property does not withstand miner bribery attacks, which can distort DECOR+ protocol incentives. This restriction also applies to any platform that  provides “Turing-complete” virtual machines, such as Ethereum.

How do you prevent from miners not verifying the parent block to create child blocks faster? (a.k.a. “SPV mining”)

RSK Labs has published an RSKIP that increases the speed of propagation and verification of blocks. This reduces the incentive to start mining a child block without proper parent block verification. The DECOR+ protocol reward miners even if they keep mining sibling blocks for a few seconds until they are ready to create a child block.

Also RSK Labs published an RSKIP allowing for the creation of child blocks even when the parent block has not be fully verified, for up to two block in a row. However reducing the network propagation time seems to be the best approach.

Why would Bitcoin miners mine the RSK blockchain?

The merge-mining functionality allows Bitcoin miners to mine in both chains with almost no extra cost. Therefore merger-miners can collect extra revenues from RSK transaction fees.  and allow them to participate in the smart contracts business.


Does RSK mining consume more electricity ?

Merge-mining is a process by which Bitcoin miners can mine both Bitcoin and RSK at the same time, with the same hardware and consuming the same electricity. RSK merge-mining uses the same cryptographic hash function as Bitcoin (SHA256).

How secure RSK merge-mining is?

RSK merge-mining is in the overall design as secure as Bitcoin mining, but assumes a stronger property from SHA256, which is “freestart collision security” of at least 100 bits. This is because RSK uses a property of the Merkle–Damgård construction to compress the size of the SPV proof.

How is the RSK blockchain secured?

RSK blockchain is secured by merge mining, with some additional security measures. The RSK blockchain is mined by the Bitcoin miners, which is the largest and most reliable blockchain network in the world. Currently, more than 35% percent of the Bitcoin hashrate is also merge-mining RSK. On top of this, RSK Labs published an RSKIP that proposes that a set of notaries (some of the most renowned and trusted Bitcoin companies) can provide an extra layer of security by issuing checkpoint notifications on the blockchain. Nodes are not forced to follow the checkpoints, but can use this information to detect network-wide attacks and enter a safe mode. This subsystem sacrifices liveness to increase safety, and can be compared to Bitcoin’s original alert system, but in case of RSK it’s federated, rather than centralized, as in Bitcoin.

What is the 2-Way Peg?

The 2-Way peg is said to be a method to transfer BTC into RBTC and vice-versa. In practice, when BTC are exchanged for RBTC, no currency is “transferred” between blockchains. There is no single transaction that does the job. This is because Bitcoin cannot verify the authenticity of balances on another blockchain. When a user intends to convert BTC to RBTC, some BTC are locked in Bitcoin and the same amount of RBTC is unlocked in RSK. When RBTC needs to be converted back into BTC, the RBTC get locked again in RSK and the same amount of BTC is unlocked in the Bitcoin blockchain. A security protocol ensures that the same Bitcoins cannot be unlocked on both blockchains at the same time. This requires transaction finality, and that’s the reason the peg required hundreds of block confirmations for transactions that unlock BTC or RBTC.

How does the peg work?

When a Bitcoin user wants to use the 2-Way Peg, he sends a transaction to a multisig wallet whose funds are secured by the Federation. The same public key associated with the source bitcoins in this transaction is used on the RSK chain to control the Smart Bitcoins. This means that the private key that controlled the Bitcoins in the Bitcoin blockchain can be used to control an account on the RSK chain. Although both public and private keys are similar, each blockchain encodes the address in a different format. This means that the addresses on both blockchains are different.


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