Coming November 15th, eCash will activate a Real-Time Target (RTT) difficulty algorithm to address irregular block times encountered by Proof-of-Work (PoW) networks. By discouraging disruptive switch mining behavior, block production times are smoothed out, which ensures faster and more predictable transaction processing for everyone using the network. This RTT algorithm leverages eCash’s Avalanche integration to provide an ideal solution to a long-lasting challenge for Bitcoin-like chains.

The Problem: Volatile Difficulty Adjustment

In PoW networks like eCash, the Difficulty Adjustment Algorithm (DAA) is used to adjust the difficulty of mining blocks relative to the incoming hashrate from miners in the system. This difficulty adjustment keeps the average block production time at around 10 minutes. However, because eCash shares its hashing algorithm with other sha256 PoW chains like Bitcoin (BTC) and Bitcoin Cash (BCH), many miners tend to switch between them based on how profitable it is to mine on one network relative to the other.

Unfortunately, this switch mining tends to create inconsistent block times. For example, when eCash’s mining difficulty is relatively low, miners from other chains temporarily shift their hash power to mine on it, exploiting the lower difficulty. Following their incentives, they come in with significantly more hashrate to mine several blocks in quick succession, what we describe as turbo blocks. In response to this influx of hashrate, the DAA raises the difficulty level. Once the network has adjusted to the higher hashrate, miners can’t mine turbo blocks anymore and switch back to other chains, leaving eCash with a high mining difficulty and a significantly smaller hashrate to solve it. Now, diametrically to the preceding turbo blocks, the network has to go through long delays between blocks for the DAA to lower the difficulty again. This may sometimes take up to hours. The result of all this switch mining is periods of unpredictable deposit times until things adjust slowly back to normal again.

This issue exists on every PoW chain to some extent, including BTC, but is more significant on chains with a minority hashrate like BCH or XEC. Miners are incentivized to switch mine like this because it’s more profitable, so though the consequences are not ideal, this behavior is expected.

The Solution: Real-Time Targeting

The Regular Heartbeat upgrade is inspired by the Real-Time Block Rate Targeting paper by Tom Harding. Heartbeat introduces a responsive algorithm on top of the current DAA that dynamically adjusts the mining target in real-time based on the elapsed time since recent blocks were received. By rejecting blocks that are mined much faster than the intended 10-minute interval, miners are disincentivized from exploiting a low difficulty to mine turbo blocks. The current DAA works well under normal conditions, so the additional Heartbeat layer focuses on specifically mitigating the disruptive switch mining behavior. This way, the base DAA never over-adjusts to begin with, removing the subsequent mismatch of high mining difficulty and low hashrate that would lead to longer than average confirmation times.

How Heartbeat’s Real-Time Targeting Works

The Heartbeat upgrade has been implemented without changes to the base consensus rules, by leveraging Avalanche Post-Consensus to dynamically add a second RTT difficulty on top of the base consensus difficulty. Each node continuously adjusts this difficulty between blocks based on the time it receives the previous block headers and the time a new block is received. The difficulty starts off very high and reduces over time until it matches the default DAA again.

After a block is accepted in an initial phase, it undergoes an Avalanche polling process to check if it also satisfies the new RTT difficulty rule. This allows nodes to confirm their position with other stakers on the network. If there’s disagreement, a node can flip its stance and accept or reject the block based on the majority decision. This way, Avalanche is used to reconcile the final block decision across the network, without altering the block header or interfering with Nakamoto consensus.

Various networks have deployed different DAA solutions with limited success for minority PoW chains. Real-time targeting traditionally runs into issues since it relies on each node's subjective timing measurements. Avalanche makes a real-time difficulty targeting approach possible since it provides a consensus mechanism to reconcile these subjective views of block times. This approach offers an ideal solution to the DAA volatility issue.

The Benefit: A Smoother Experience for Everyone

While Regular Heartbeat provides technical advantages in stabilizing block times and curbing the volatility caused by switch miners, the most important benefit is the improved user experience.

With blocks being produced at a more regular rate, eCash users benefit from faster transaction confirmations. This is especially important for users who rely on quick deposit times. As blocks come in closer to the 10-minute target, users can trust that their transactions will be confirmed shortly. Heartbeat improves eCash’s 1-block finality experience, reducing waiting times and friction to a minimum in everyday transactions.

Heartbeat also makes the network more predictable. The eCash network becomes more efficient, reliable, and user-friendly. Knowing that blocks will be processed consistently is an improvement for miners, merchants, exchanges, developers, and regular users.

Conclusion: Healthy, Strong, Competitive

With Regular Heartbeat, eCash is optimizing PoW to operate with a steady pulse—one block about every ten minutes, just as intended. Considering XEC transactions are securely settled after just one confirmation, as opposed to six or more confirmations like on BTC, this upgrade already marks a significant improvement.

But this is just the beginning. Another game-changer in its final development stages is Avalanche Pre-Consensus. This upgrade will introduce instant finality, securely settling transactions within 2 seconds, irrespective of block confirmations. With healthy block times and strong double-spend protection, eCash solidifies its position as one of the most reliable, secure, and fastest L1s in the crypto space.