Topic: | Nxt | Blockchain Platform | Proof of Stake | Official - page 211. (Read 941285 times)

Example 3.0.2. The cryptoeconomically secure entropy source used in NXT[16] is dened recursively as follows:
 E(G) = 0
 E( +) = sha256(E()+V ()) where V () is the block proposer of

Assumption 3.1. For any time internal I, there exists some xed probabil-ity po(I) such that a node randomly selected according to the weight functionused to measure a cryptoeconomic state machine's Byzantine fault tolerancecan be expected to be oine for at least the next I seconds starting from anyparticular point in time with at least probability po.Note. We can derive the above assumption from an altruism assumption bysimply stating in the protocol that nodes \should" randomly drop oinewith low probability; however, in practice it is simpler and cleaner to relyonly on natural faults.Note. Combining the two uninuenceability criteria into one (\it is impos-
sible to increase the probability of P from p to p  (1+k) without expendingat least b L k resources") is likely very dicult; it is hard to avoid having
ways to cheaply multiply the probability of low-probability predicates byonly acting when you are sure that your action will have an inuence on theresult.
......

Lemma 3.0.3. The NXT algorithm described above satises the conditionsfor being a cryptoeconomically secure entropy source.Proof. To prove unpredictability, we note that the NXT blockchain pro-duces a block every minute, and so the update v   sha256(v; V ()) takesplace once a minute. During each round of updating, there is a probabil-ity 1 ...........