What is Security budget?
Total miner revenue — subsidy plus fees — which sets how expensive it would be to attack the chain.
Attacking Bitcoin means out-mining it, so the cost of an attack scales with what honest miners are collectively earning and spending.
As the subsidy halves toward zero, fees must carry a growing share of this budget. Whether a fee market alone can sustain adequate security is a genuinely open question, and one of the more interesting long-run problems in the design. We treat it as open, not settled in either direction.
Related terms
Block subsidy
The newly issued bitcoin paid to the miner of each block. It began at 50 BTC and halves every 210,000 blocks.
Transactions & feesFee rate (sat/vB)
What a transaction pays per virtual byte of the space it occupies. Miners prioritise by fee rate, not by…
Network51% attack
An attack in which someone controlling a majority of hashrate reorganises recent blocks to reverse their own…
EconomicsHalving
The scheduled 50% reduction of the block subsidy, occurring every 210,000 blocks — roughly every four years.
This definition is part of the Bitcoin Logical glossary. For the fuller explanation, start with Learn, or see the live numbers on The Bitcoin Signal.