Stratum
Also: Stratum V1, Stratum V2
mining · advanced
The protocol miners use to talk to pools — and, in V2, to construct their own block templates instead of accepting the pool's.
Stratum V1 (2012) is the protocol every modern ASIC speaks to a mining pool. The pool sends a block template and a difficulty target; the miner hashes, returns shares as proof-of-work, and the pool credits the miner's account. When a share happens to also satisfy the network target, the pool broadcasts the block and pays out the reward.
The flaw V1 has is structural: the pool picks which transactions go into the block. Miners just hash whatever template they get. This concentrates censorship power in a handful of pool operators, even though the actual hashing is decentralized.
Stratum V2 (Braiins, Square, others, 2022) restores miner control. With "Job Negotiation," the miner builds its own template — picks transactions, sets the coinbase output — and the pool just validates and aggregates shares. Adoption is gradual; the protocol also adds encryption and bandwidth improvements.