StateLeaf

A state leaf represents a user's participation declared through an identity (their public key) and information relevant to their ability or right to cast votes in a poll (their voice credit balance and the block timestamp at which they signed up).

We define a state leaf $sl$ as the $poseidon_4$ hash of the following:

Symbol	Name	Comments
$sl_{P_x}$	Public key's x-coordinate
$sl_{P_y}$	Public key's y-coordinate
$sl_{v}$	Voice credit balance
$sl_{t}$	Block timestamp	In Unix time (seconds since Jan 1 1970 UTC)

The hash $sl$ is computed as such:

$sl = poseidon_4([sl_{A_x}, sl_{A_y}, sl_{v}, sl_{t}])$

Blank state leaf

A blank state leaf $sl_B$ has the following value:

$6769006970205099520508948723718471724660867171122235270773600567925038008762$

This value is computed as such:

$A_{b_x} = 10457101036533406547632367118273992217979173478358440826365724437999023779287$ $A_{b_y} = 19824078218392094440610104313265183977899662750282163392862422243483260492317$ $sl_B = poseidon_4([A_{b0}, A_{b1}, 0, 0])$

The code to derive $A_{b_x}$ and $A_{b_y}$ is here. The function call required is pedersenHash.getBasePoint('blake', 0)

1. Hash the string PedersenGenerator_00000000000000000000000000000000_00000000000000000000000000000000 with $blake_{256}$. In big-endian hexadecimal format, the hash should be 1b3ef77ef2cd620fd2358e69dd564f35556aad552fdd7f06b777bd3a1d697160.
2. Set the 255th bit to 0. The result should be 1b3ef77ef2cd620fd2358e69dd564f35556aad552fdd7f06b777bd3a1d697120.
3. Use the method to convert a buffer to a point on the BabyJub curve described in [2.3.2].
4. Multiply the point by 8. The result is the point with x-value $A_{b_x}$ and y-value $A_{b_y}$

Given the elliptic curve discrete logarithm problem, we assume that no one knows the private key $s \in {F}_p$ and by using the public key generation procedure in [1.4], we can derive $A_{b_x}$ and $A_{b_y}$. Furthermore, the string above (PedersenGenerator...) acts as a nothing-up-my-sleeve value.