Editing Yarrow algorithm (section)

===Yarrow-160===
The Yarrow uses two important algorithms: a [[cryptographic hash function|one-way hash function]] and a [[block cipher]]. The specific description and properties are listed in the table below.
{| class="wikitable"
|-
! Algorithms !! Properties !! What Yarrow-160 uses
|-
| Hash function h(x) ||
* One-way
* m-bit output size
* collision intractable
Given {{var|M}} input values, the |M| selections of output values are uniformly distributed over ''m''-bit values. 
|| [[SHA-1]] hash function
|-
| Block cipher E() ||
*Resistant to known-plaintext and chosen-plaintext attacks
High statistical performance of outputs when given highly patterned inputs. 
|| Three-key [[Triple DES]]
|}

====Generation====
[[File:Functions for Generation Mechanism.png|thumb|Functions for generation mechanism]]
Yarrow-160 uses three-key [[Triple DES]] in counter mode to generate outputs. ''{{math|C}}'' is an ''n''-bit counter value; ''{{math|K}}'' is the key. In order to generate the next output block, Yarrow follows the functions shown here.

Yarrow keeps count of the output block, because once the key is compromised, the leak of the old output before the compromised one can be stopped immediately. Once some system security parameter ''{{math|P<sub>g</sub>}}'' is reached, the algorithm will generate ''{{math|k}}'' bits of PRNG output and use them as the new key. In Yarrow-160, the system security parameter is set to be ''10'', which means ''{{math|P<sub>g</sub> {{=}} 10}}''. The parameter is intentionally set to be low to minimize the number of outputs that can be backtracked.

====Reseed====
The reseed mechanism of Yarrow-160 uses SHA-1 and Triple DES as the hash function and block cipher. The details steps are in the original paper.

====Implementation of Yarrow-160====
Yarrow-160 has been implemented in [[Java (programming language)|Java]], and for [[FreeBSD]]. The examples can be found in "An implementation of the Yarrow PRNG for FreeBSD"<ref>{{cite web|url=https://www.usenix.org/legacy/events/bsdcon02/full_papers/murray/murray_html/|title=An implementation of the Yarrow PRNG for FreeBSD|access-date=18 October 2016}}</ref> by Mark R. V. Murray.