Miden's Privacy Chain Goes Live—With Caveats

The a16z-backed Polygon spin-off opens a partner mainnet where your phone proves transactions, but validators can still see your inputs.

By The crypto-money Desk

Miden, the a16z-backed privacy chain that spun out of Polygon last year, opened its partner mainnet on October 26. [1] Invited users can now move real funds for the first time, through Bread, a self-custodial wallet available on iOS, Android, and Chrome. [1][2]

The architecture is device-first: your phone runs each transaction and proves it using STARKs, a type of zero-knowledge proof that relies only on hash functions. [1] The chain stores just commitments—hashes—of private account data, and co-founder Bobbin Threadbare says most transactions can be proven in under three seconds on a phone. [1]

Privacy, however, is partial. [1] Validators also store threshold-encrypted transaction details that a group of them could decrypt "during extraordinary events (e.g., hacks)." Swaps are public for now, too. [1] Balances are capped below $1,232.462—a nod to the "Goldilocks" prime Miden uses under the hood—and wallets arrive pre-funded with USDCx to cover fees. [1][2]

The tension between safety and genuine privacy is the defining design problem of this era in cryptography. Miden is making that tension visible rather than papering over it.

This phase is explicitly temporary. Users must withdraw before a reset whose deadline hasn't been announced. [1] Public mainnet, which Threadbare places a few months out, will swap the Poseidon2 hash function for a Blake3-based one—confidence in Poseidon2 has been shaken—and will add full ZK block proofs and a more mature fee model. [1]

Miden's advice to anyone joining: only use funds you can afford to lose. [1] For a network stress-testing the boundary between transparency and privacy, that caveat is also the point.

activity is hidden from the public but not from validatorsBobbin Threadbare