Editing Yarrow algorithm (section)

===Components===
The design of Yarrow consists of four major components: an [[Entropy (computing)|entropy]] accumulator, a [[Random seed|reseed]] mechanism, a generation mechanism, and reseed control.

Yarrow accumulates entropy into two pools: the fast pool, which provides frequent reseeds of the [[Unique key|key]] to keep the duration of key compromises as short as possible; the slow pool, which provides rare but conservative reseeds of the key. This makes sure that the reseed is secured even when the entropy estimates are very optimistic.

The reseed mechanism connects the entropy accumulator to the generating mechanism. Reseeding from the fast pool uses the current key and the [[Hash value|hash]] of all inputs to the fast pool since startup to generate a new key; reseeding from the slow pool behaves similarly, except it also uses the hash of all inputs to the slow pool to generate a new key. Both of the reseedings reset the entropy estimation of the fast pool to zero, but the last one also sets the estimation of the slow pool to zero. The reseeding mechanism updates the key constantly, so that even if the key of pool information is known to the attacker before the reseed, they will be unknown to the attacker after the reseed.

The reseed control component is leveraging between frequent reseeding, which is desirable but might allow [[#Iterative guessing attack|iterative guessing attacks]], and infrequent reseeding, which compromises more information for an attacker who has the key. Yarrow uses the fast pool to reseed whenever the source passes some threshold values, and uses the slow pool to reseed whenever at least two of its sources pass some other threshold value. The specific threshold values are mentioned in the [[#Yarrow-160|Yarrow-160]] section.