Stellar has added support for Zero-Knowledge Proofs through BLS12-381 elliptic curve integration and is implementing BN254 support via CAP-0074, with the upcoming X-Ray protocol upgrade also adding Poseidon hash functions (CAP-0075) to enable efficient ZK applications on Soroban.
This technical deep-dive explores Stellar's implementation of Zero-Knowledge Proof capabilities through host functions in Soroban smart contracts. The article explains how Stellar added BLS12-381 elliptic curve support in 2024 and is actively implementing BN254 support to enable developers migrating existing ZK applications. The upcoming X-Ray protocol upgrade introduces two critical CAPs: CAP-0074 for BN254 host functions and CAP-0075 for Poseidon hash functions. These additions provide the cryptographic primitives needed for efficient, privacy-preserving applications while maintaining blockchain transparency. The dual-curve approach allows developers to choose between BLS12-381's superior security (128-bit) and BN254's compatibility with existing EVM-based ZK ecosystems, while Poseidon addresses the performance bottleneck of traditional hash functions in ZK circuits.