Quantum-Ready Blockchains Compared, Part 3: Built to Swap — Algorand, Nervos, Aptos and Sui

Disclosure: I hold CKB. This series presents information, not recommendations, and nothing in it is investment advice. Previously: Part 1 set out five tests and a seven-rung readiness ladder. Part 2 looked at QRL, the only chain that was quantum-safe from its first block, and what that cost it in signature size, convenience and scale. QRL built quantum safety in before launch. The four chains in this part took a different route: they built the ability to change . Each was designed so that the cryptography protecting an account is not welded to the account itself and can be swapped out later without splitting the network. That is the family most likely to describe itself as quantum-ready, and the description is partly fair. The machinery really exists. But the four chains are at very different points with it. Algorand has shipped it into its most popular wallet. Nervos has shipped it into exactly one wallet. Aptos has written it, merged it and left it switched off. Sui is testing it. And all four share a second question that their announcements rarely raise: what about the rest of the chain? The short version: being built to swap solves the hardest engineering problem, and leaves two others behind, getting holders to actually swap, and, on staking chains, swapping the consensus too. The idea: separate the key from the account On Bitcoin and Ethereum as originally designed, an account and the elliptic-curve key that controls it are close to the same thing. Changing the kind of signature means changing what an account is , which is why upgrades there need network-wide agreement. The chains in this part pulled the two apart. Each in its own way lets the network check a signature of whatever kind the account specifies . Add a new signature scheme to the menu, and holders can choose it. Nobody's old account breaks, and nobody has to agree to a network split, known as a hard fork . The four chains do this differently, and the difference shows up in a very practical place:…