Before we debate the feasibility of Bitcoin L2, it's helpful to define what Bitcoin L2 is? In my view L2 is a layer built on top of X to make X more "powerful", e.g. more scalable, more programmable, more privacy, etc. "A L2 is a layer as secure as L1" is simply an illusion. Extra layers introduce extra security assumptions and implementation bugs - you can still lose money in Lightning or optimistic rollups, e.g when you want to close channel or challenge/escape while L1 is in congestion. ZK rollups have different problems like more assumptions and unclear prover incentive design. Only L1 is as secure as L1. The compromise on security is the exact reason why L2s are more "powerful". So the right question is not if L2 is as secure (they're not), but how much less secure and how much more powerful? Different L2s make different choices, some are worse than others because they sacrificed a lot for little value in return. Some are just different preferences on trade-offs. Bitcoin L2 is even more interesting because in this case the X can refer to both 1. the PoW driven Bitcoin ledger, and 2. the BTC asset/currency/money. CKB is less secure/decentralized than the Bitcoin ledger, but as a 4 year-old PoW chain it's much more secure/decentralized on its own than recent L2s who try to "borrow" security from L1 (for L2s "security borrowing" is more like a fast bootstrapping strategy rather than a requirement). CKB extends UTXO model to bring more value and programmability to BTC, make BTC more powerful. CKB is UTXO based also means it could work well with other Bitcoin L2 technologies like Lightning/RGB/Taproot assets/inscriptions (yeah I consider client-side validation protocols a kind of L2). p.s. I use "secure/security" for short, L2s could compromise on decentralization (can read as "censorship resistance") too.

CKB Is An Ideal Bitcoin Layer 2 As a monetary system, Bitcoin is inherently layered. But what should a Bitcoin monetary layer 2 look like? It should be an integral part of the entire system, sharing the same foundational values and design decisions. Ideally, it would be interconnected with layer 1, allowing for free BTC flow between layers, and offering a consistent user experience for both users and developers. CKB is the ideal monetary layer 2 for Bitcoin. CKB shares Bitcoin values, e.g. PoW not PoS, UTXO not Account, decentralization over TPS, no issuance manipulation, etc. With Cell, an extended UTXO model, CKB can provides more decentralized use cases for Bitcoiners while maintaining a consistent user and developer experience. Imagine operating CKB applications with a Bitcoin wallet, rotating addresses for privacy, and managing UTXOs under dust limit / minimum capacity constraints - all underpinned by the same foundational principles. Moreover, CKB is an excellent experimental ground for Bitcoin, provides an enhanced UTXO model with stronger programming capabilities while upholding Bitcoin's core values and design philosophy. This means CKB faces challenges akin to those of Bitcoin, with optimal solutions potentially benefiting both. The ability to use customized cryptographic primitives on CKB empower developers and researchers to explore their most innovative ideas. On CKB, it's easier to test new ideas like covenant (CTV), PSBT and Intents, which, if successful, could be integrated back into Bitcoin Layer 1. Importantly, a monetary layer 2 doesn't need to share security with Bitcoin. Multiple monetary layer 2s can form a more decentralized, resilient, and loosely connected monetary system with Bitcoin at its core. This system wouldn't have a single point of vulnerability in terms of security, and it would offer consistent user experience without liquidity fragmentation seen elsewhere. Because Bitcoin is money, it only needs to provide monetary functions, not everything else. Because UTXO is the first-class citizen here, accounts are abstracted away and managed off-chain. #CKB aligns perfectly with this vision, making it an ideal #Bitcoin #Layer2 .

For interested readers, here're some real progresses on AA and quantum security instead of cheap talks - joy.id/ - github.com/cryptape/quantum-…