HOW CROSSLINK WORKS
A TECHNICAL DEEP DIVE
INTO HYBRID CONSENSUS
THE FINALITY PROBLEM
All PoW chains face this risk. Crosslink eliminates it.
Try sending a transaction, then attack the chain.
Send a transaction to begin
Most mid-cap PoW chains cost $2K-$10K/hr to attack via NiceHash rental.
→ Crypto51 Attack CalculatorBitcoin requires 6 confirmations (~60 min) for high-value deposits. Exchanges enforce this for reorg protection.
→ Kraken Deposit TimesDocumented losses: BTG (~$18M), ETC (~$10M+), and numerous smaller attacks. Many go unreported by exchanges.
→ MIT 51% Attack Research
THE FORGE
Proof of Work
Miners expend real energy to propose blocks. This provides unforgeable costliness and censorship resistance.
THE VAULT
Proof of Stake
Finalizers vote to certify blocks. Stake from the Orchard shielded pool in quantized amounts (10ⁿ ZEC). Once sealed, history cannot be rewritten.
CROSSLINK
Two engines. One chain.
TRAILING FINALITY LAYER
"Trailing" means the finality gadget waits.
Let the dust settle before cementing the floor.
1. Observation
The gadget observes the PoW chain, allowing short-term forks to resolve naturally.
2. Voting
Once a block has sufficient confirmations, Finalizers cast votes to certify it.
3. Finalization
When 2/3 agree, history is locked. No amount of hashrate can revert it.
TENDERLINK
The custom-built consensus engine.
Not a fork. Not an off-the-shelf solution. Purpose-built for Zcash.
1. Propose
A finalizer proposes the next block to be finalized from the PoW chain.
2. Prevote
Finalizers broadcast prevotes. Need ⅔ supermajority to proceed.
3. Precommit
After seeing ⅔ prevotes, finalizers broadcast precommits.
4. Commit
With ⅔ precommits, the block is deterministically finalized. Irreversible.
THE DUAL HURDLE
Attacking legacy Zcash required only hashrate.
Attacking Crosslink requires hashrate AND stake.
Hurdle 1: Hashrate
Requires controlling 51% of global Equihash power. Expensive, but theoretically rentable.
Hurdle 2: Stake
Requires acquiring >2/3 of all staked ZEC. Impossible to hide, and destroyed upon detection.
"Attacks aren't just difficult—they're financially suicidal."
CONTINGENCY MODE
What happens if the finality layer fails?
Crosslink fails OPEN, not closed.
PURE PoS FAILURE
- Blocks stop being produced
- Users stranded
- Exchange deposits stuck
CROSSLINK FALLBACK
- PoW block production continues
- Probabilistic finality (wait for confirmations)
- Coinbase-only mode available*
- BFT finality auto-resumes
*Coinbase-Only Restriction: During prolonged BFT outages, the protocol may enforce a mode where only mining reward transactions are processed. This prevents double-spend attempts while maintaining chain liveness until finality is restored.
"Safety degrades gracefully. The chain never stops."
HYBRID CONSTRUCTION
The Ebb-and-Flow model: two ledgers, one protocol.
Always available. Eventually final.
Available Ledger
PoW provides continuous block production. Always live, even during network partitions.
Finalized Prefix
BFT finalizes a trailing portion of the PoW chain. Once final, blocks cannot be reverted.
The Ebb-and-Flow Property
Resolves the availability-finality dilemma: no single ledger can be both always available AND always safe.
- PoW: Available under dynamic participation
- BFT: Safe under network partitions
- Combined: Best of both worlds
FINALITY COMPARISON
Send a transaction and watch how each system reaches finality.
Speed matters, but so does reliability.
Pure PoS is fastest, but halts during network partitions.
Crosslink delivers assured finality while maintaining liveness guarantees.
| Metric | Legacy Zcash | Crosslink | Pure PoS |
|---|---|---|---|
| Time to Finality | ~60 minutes | ~1 minute (target) | ~12 seconds |
| Finality Type | Probabilistic (Nakamoto) | Assured (Deterministic BFT) | Deterministic (BFT) |
| Sybil Mechanism | Energy + Hardware | Energy + Capital | Capital only |
| Reorg Resistance | Vulnerable to deep reorgs | Immune past finality | Vulnerable to long-range |
| Liveness (Partition) | High (chain grows) | High (PoW fallback) | Low (halts) |
| 51% Attack Cost | Low (rental) | High (hash + stake) | Stake acquisition |
| Consensus Privacy | N/A (miners anon) | High (quantized staking) | Low (public validators) |
BRIDGING WITHOUT FEAR
Trust-minimized bridges require mathematical certainty.
Zcash becomes the privacy layer for ALL of DeFi.
Zcash Shielded Assets
Bridge USDC into zUSDC. Trade privately. Bridge out.
Cross-Chain Swaps
Swap ZEC ↔ ETH with instant settlement, no reorg risk.
Chain Abstraction
Zcash integrates with NEAR's Intents. Solvers settle instantly.