Nervos CKB (Common Knowledge Base) is a public blockchain described in a 2019 whitepaper by Jan Xie and the Nervos Foundation. CKB makes two foundational design choices that distinguish it from other smart contract platforms:

1. The Cell Model: A generalization of Bitcoin’s UTXO model where each “cell” is an arbitrary data container with owner-determined logic — enabling general computation while preserving Bitcoin’s UTXO security properties.

1. State storage tokenomics: CKBytes (the native token) represent the right to occupy bytes of on-chain state. Storing 1 byte of state requires holding 1 CKByte. This directly solves state bloat: storage is finite and scarce, priced by the market.

CKB serves as the Layer 1 of the Nervos Network — a preservation and settlement layer. Higher-level computation is intended to happen on Layer 2 systems (payment channels, sidechains) anchored to CKB.

> Specification: github.com/nervosnetwork/rfcs/blob/master/rfcs/0002-ckb/0002-ckb.md

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Publication and Context

By 2019, the “state explosion” problem in account-model blockchains was evident. Ethereum’s state size had grown to hundreds of gigabytes, and most of this state paid no ongoing cost — once stored by a contract, data persisted indefinitely at no charge. This created a tragedy of the commons: storing state was cheap for users but costly for all validators in perpetuity.

Bitcoin avoided this problem by design: UTXOs, once spent, are removed from the active set. But Bitcoin’s UTXO model cannot easily support general computation.

CKB’s thesis: design a Layer 1 that has Bitcoin’s UTXO security and Ethereum’s expressiveness, while solving the state storage economic problem through the CKByte scarcity mechanism.

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The Cell Model

A Cell is CKB’s fundamental data unit. Every cell has:

Field	Description
capacity	Number of CKBytes locked; defines maximum data size
data	Arbitrary bytes — can be anything (token balances, code, NFT metadata)
lock script	Defines ownership (who can consume this cell)
type script	Optional; defines validation rules for the cell’s data

Comparison to Bitcoin UTXO:

• A Bitcoin UTXO has a fixed value (satoshis) and a scriptPubKey (locking script)
• A CKB Cell generalizes this: capacity replaces value, and data allows arbitrary state

Transactions consume cells as inputs and create cells as outputs — identical to Bitcoin’s UTXO model. This preserves all of Bitcoin’s security properties (no global state mutation, parallel validation, no transaction ordering dependence within a block).

Scripts as cells: The lock and type scripts themselves are stored in cells. A script cell is referenced by its hash in other cells. This enables script upgrades: deploying a new version of a script is just creating a new cell; existing cells can reference either version.

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CKB-VM: RISC-V Virtual Machine

The CKB-VM executes lock and type scripts:

• Instruction set: RISC-V (open standard; hardware implementations widely available)
• Language agnostic: Any language that compiles to RISC-V works on CKB — C, Rust, JavaScript (via WASM-to-RISC-V), and more
• Formal verification: RISC-V’s simplicity and open specification enable formal verification of the VM itself
• No precompiles: Unlike EVM (which has hash function precompiles), CKB scripts are just code; common operations are library cells referenced by hash

This is highly flexible: CKB can support new cryptographic primitives (quantum-resistant signatures, custom hash functions) by deploying a new script cell, without a protocol upgrade.

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Eaglesong: Custom Proof of Work

CKB uses Eaglesong, a custom hash function designed specifically for CKB mining:

• Designed to make ASIC manufacturing available to a broad range of manufacturers (not dominated by a single company)
• Sponge construction similar in structure to SHA-3 but optimized differently
• Replaces the original Cuckoo Cycle PoW used in testnet

Block time: 10 seconds target.

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CKByte Tokenomics: State Rent Without Rent

The fundamental insight: holding CKBytes represents capacity to store state.

• To store 100 bytes in a cell, you must have capacity ≥ 100 CKBytes locked in that cell
• You cannot spend those CKBytes while the cell exists — they are “occupied”
• When the cell is consumed (destroyed), you reclaim the CKBytes

This is not traditional state rent (periodic payment). Users pay the opportunity cost of holding CKBytes (they cannot use them for other purposes) rather than an explicit fee. The network collects no ongoing fee.

Secondary issuance: CKB has a secondary (inflationary) issuance schedule. A portion of this inflation goes to miners; the rest (“state miners” share) goes to a treasury called the Nervos DAO. CKByte holders can lock tokens in the Nervos DAO to receive the secondary issuance proportionally, effectively neutralizing inflation for long-term holders. Unredeemed DAO earnings are burned.

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Reality Check

CKB’s Cell model and storage tokenomics are genuinely innovative solutions to real blockchain design problems. The state explosion solution is theoretically elegant.

In practice:

• Adoption has been limited. Developer tooling and ecosystem around RISC-V and CKB-VM require significant learning compared to EVM.
• Layer 2 ecosystem is nascent. CKB’s value proposition depends largely on L2 activity settled to L1; this ecosystem remained small.
• RGB++ interest: In 2024, CKB gained renewed attention as RGB++ (an extension of the Bitcoin RGB protocol) chose CKB as its smart contract layer, potentially bringing Bitcoin-native asset issuance to CKB.
• Market cap underperformance: CKB has consistently been a small-cap project relative to its technical sophistication.

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Legacy

Nervos CKB is one of the most technically sophisticated UTXO-model smart contract platforms built. Its state storage tokenomics directly address what many researchers consider a core long-term scaling problem. The RGB++ integration (2024) gave CKB a potential path to relevance in the Bitcoin ecosystem.

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Related Terms

• UTXO
• Cell Model
• State Bloom
• Proof of Work

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Research

• Xie, J., et al. (2019). Nervos CKB: A Common Knowledge Base for Crypto-Economy. Nervos Foundation RFC-0002.

— Primary specification; describes the Cell model, CKB-VM, Eaglesong PoW, and CKByte storage tokenomics.

• Nakamoto, S. (2008). Bitcoin: A Peer-to-Peer Electronic Cash System. bitcoin.org.

— CKB’s Cell model directly extends Bitcoin’s UTXO model; Nervos explicitly cites Bitcoin as the primary design inspiration.

• Wood, G. (2014). Ethereum: A Secure Decentralised Generalised Transaction Ledger. ethereum.github.io.

— Ethereum’s account/world-state model; CKB’s design is in part a response to the state explosion problem this model creates.