Zero-knowledge (ZK) coins are the native tokens of projects that use zero-knowledge proofs in their core design. The proofs may protect transaction privacy, as in Zcash, or compress thousands of transactions into a single succinct proof, as in ZK rollups such as Starknet and zkSync. Zcash (ZEC), Polygon (POL), Starknet (STRK), and ZKsync (ZK) rank among the largest ZK coins by market capitalization.

A zero-knowledge proof is a cryptographic method. One party (the prover) creates a short proof that a statement is true. Another party (the verifier) checks the proof without seeing the underlying data. In Zcash, the prover shows that a transaction is valid without revealing the sender, receiver, or amount. In a ZK rollup, the prover shows that a batch of transactions followed the chain's rules without forcing Ethereum to replay each one.

Zcash (ZEC) is the largest zero-knowledge coin by market capitalization. It launched in 2016 and became the first major blockchain to use zk-SNARKs for shielded transactions. Eligible users can buy Zcash (ZEC) on CEX.IO with a card, SEPA transfer, Apple Pay, or another supported payment method.

SNARKs (Succinct Non-interactive Arguments of Knowledge) produce small proofs that verify quickly but usually require a trusted setup ceremony. STARKs (Scalable Transparent Arguments of Knowledge) produce larger proofs and need no trusted setup. STARKs rely on hash-based cryptography that holds up against quantum computers. zkSync Era and Polygon zkEVM use SNARK-based proofs. Starknet uses STARK proofs.

A ZK rollup is a Layer-2 chain that batches transactions and posts a single validity proof back to Ethereum. The proof shows that every transaction in the batch followed the rules. Ethereum verifies the proof in milliseconds and accepts the entire batch as final. ZK rollups cut fees and raise throughput while inheriting Ethereum's security.

Starknet is a ZK rollup on Ethereum that uses STARK proofs. The network targets high throughput and low fees. Apps deploy in Cairo, a programming language designed for STARK-friendly computation. STRK is the network's native token and pays for transaction fees and protocol governance.

zkSync Era is a ZK rollup on Ethereum from Matter Labs. The network targets EVM compatibility, so Ethereum apps can deploy with minimal changes. ZK is the native token of the protocol and votes on protocol upgrades through the ZKsync governance system.

Eligible users can buy zero-knowledge coins on both centralized and decentralized exchanges. Centralized exchanges, such as CEX.IO, support fiat payments and offer trading pairs in major currencies. Decentralized exchanges allow direct on-chain swaps but require an external wallet and self-custody.

Instant Buy is the fastest way to buy zero-knowledge coins on CEX.IO. Eligible users can buy Zcash (ZEC), Polygon (POL), Starknet (STRK), ZKsync (ZK), and other supported ZK tokens with a credit/debit card, SEPA, Apple Pay, Google Pay, Skrill, or another method available in their region. Each verified user receives a free crypto wallet.

Users can hold ZK coins in custodial or non-custodial wallets. Non-custodial wallets keep the private keys on the user's own device. CEX.IO provides a free custodial wallet to every verified user. The wallet supports ZEC, POL, STRK, ZK, and other listed ZK tokens within one interface. Zcash-specific non-custodial wallets such as Zashi manage shielded addresses for users who want full privacy features.