Quote from: Gavin Andresen on February 02, 2014, 05:10:20 PM

Okey dokey... so how do fees work in Ethereum?

Or do you have some other clever distributed way of preventing flood-the-system-with-bogus-contracts DoS attacks?

Here's the relevant part of my post above highlighted for clarity:

In Ethereum, you have entities called contracts, where contracts have their own balances, and are activated every time you send a transaction (think: money with an optional message attached) to them. The contract has 16 computational steps for free to give it wiggle room to determine whether a transaction is even worth processing; after this, every computational step that the contract takes costs it 1x BASEFEE (or more for specialized data access or crypto ops). If the contract goes bankrupt halfway through the computational process, it just stops halfway through.

Quote from: k99 on February 02, 2014, 06:33:15 PM

A contract is associated with a balance. If the balance is 0 the contract will not be executed. A contract gets executed by sending a transaction to a contract. The tx needs to be funded, so I assume you cannot send a 0 Ether tx to a contract.

Actually, you can send a 0 ether tx to a contract, although that tx will still cost the sender a TXFEE.

Quote from: k99 on February 02, 2014, 06:33:15 PM

The tx needs to be funded with a fee to activate a contract and the contract need to have some balance get executed.

Precisely; although with the proviso that the first 16 computational steps in contract execution are free, so if a contract is decently written you can't involuntarily send transactions to it to bankrupt it.

Here's an example also (assume BASEFEE = 1 ether for convenience)

CONTRACT: [ PUSH 0 JMP ], balance: 1000

The contract is pretty much the simplest possible infinite loop script; it's the equivalent of "10: DO_NOTHING; 20: GOTO 10"

Now, suppose that someone sends it a transaction with value 10 ether (this tx will cost the sender 110 ether due to the TXFEE):

TX: [ ADDRESS, 10, [], v, r, s]

Step 1: { Counter: 0, Index pointer: 0, Stack: [], balance: 1010 }
Step 2: { Counter: 1, Index pointer: 2, Stack: [ 0 ], balance: 1010 }
Step 3: { Counter: 2, Index pointer: 0, Stack: [], balance: 1010 }
...
Step 16: { Counter: 15, Index pointer: 2, Stack: [ 0 ], balance: 1010 }
Step 17: { Counter: 16, Index pointer: 0, Stack: [], balance: 1009 }
Step 18: { Counter: 16, Index pointer: 2, Stack: [ 0 ], balance: 1008 }
...
Step 1025: { Counter: 16, Index pointer: 0, Stack: [], balance: 1 }
Step 1026: { Counter: 16, Index pointer: 2, Stack: [ 0 ], balance: 0 }
Step 1027: ERROR NOT ENOUGH FUNDS HALT

The contract now has a balance of 0 ether, so if someone tries to send that transaction again, the second time around execution will stop at step 17 rather than 1027.