hush-v3-whitepaper/hush-v3.tex

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\begin{document}

\title{\doctitle \\
\Large \docversion}
\author{
\Large \leadauthor\hairspace\thanks{\;duke@leto.net}
}
\date{\today}
\maketitle

\renewcommand{\abstractname}{}
\vspace{-8ex}
\begin{abstract}
\normalsize \noindent \textbf{Abstract.}

\Hush originally was a source code fork of the \Zcash 1.0.8 codebase. Hush was
    originally called "Zdash" and mined a genesis block on Nov 17, 2016.
The latest version of \Hush migrates to a new codebase with a new genesis
block while keeping the emission schedule as close as possible to the original
intentions

\vspace{2.5ex}
\noindent \textbf{Keywords:}~ \StrSubstitute[0]{\keywords}{,}{, }.
\end{abstract}

\vspace{-10ex}
\phantomsection
\addcontentsline{toc}{section}{\Large\nstrut{Contents}}

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\newpage

\nsection{Introduction}
\nsection{Things Staying The Same}

\begin{itemize}
\item 21M total supply
\item Block reward
\item Block time
\item Halving interval
\item Delayed-Proof-Of-Work
\end{itemize}

\nsection{Things Changing}

\begin{itemize}
    \item New Genesis Block
    \item Sprout Disabled
    \item First Pure Sapling Chain, with Super Fast Shielded Transactions
    \item s/ZEC/KMD/ as upstream
    \item New main Github repo
    \item Addition of 10\% Founders Reward
    \item Address prefix change (t1,t3 becomes R,b)
    \item RPC and P2P ports
    \item Enable CryptoConditions (Custom Consensus)
    \item Improved Difficulty Adjustment Algorithm (LWMA-jl777)
    \item Block Size increase to 4MB
    \item Shielding Rule
    \item TLS Support
\end{itemize}

\begin{quote}
    Governments can be useful to the governed only so long as inherent tendencies toward tyranny are restrained.
            - The Stolen Journals
\end{quote}

\nsection{First Pure Sapling Blockchain}

HUSH is proud to be the very first pure Sapling blockchain! HUSH enables
Sapling at Block 1, which means no Sprout UTXOs will ever exist on our new
blockchain. This removes any future risk of Sprout bugs/CVEs and drastically
reduces the maintenance cost going forward, as Sprout code and Sapling code
are different codepaths and so supporting Sprout at least doubles the amount
of code to maintain.

No other blockchain has started as a pure Sapling chain, all other existing
Zcash source code forks have transitioned from Sprout to Sapling.

\nsection{10\% Founders Reward}

HUSHv3 adds a 10\% Founders Reward, in perpetuity, until block rewards end.
This is approximately 5.5 million blocks or about 30 years.

The Founders Reward is paid out every block to a single address:

    RHushEyeDm7XwtaTWtyCbjGQumYyV8vMjn

Initially the Founders Reward is 1.25 HUSH, starting at Block 129 until the first
halving on the new chain at Block 340000.

\nsection{New Upstream: KMD}

HUSH is no longer directly a source code fork of Zcash (ZEC), it is now a fork
of Komodo (KMD). Since KMD itself is a fork of ZEC, this means we gain an
immense amount of code and features, and all the development velocity of jl777.
As an example, during the development of HUSHv3, over the course of a few weeks,
about 20,000 lines of code was changed in upstream Komodo repo, adding many
features and fixing various bugs.

We expect to see the developement velocity of the HUSH community greatly
increase, since we will now essentially have jl777 constantly doing low-level
blockchain internals coding, which frees up other developer resources to work
on wallets, explorers, HushList protocol and applications which sit on top
of the RPC interface.

HUSHv3 is a source code fork of the jl777/komodo git repository and live at

    https://github.com/MyHush/hush3

As of Block 500,000, the legacy Hush network and codebase is unsupported.  The
network is not being forcibly turned off, those that want are free to use it,
and use any encrypted data they may have in memo fields.

\nsection{CryptoConditions}

CryptoConditions are UTXO-based smart contracts and also an IETF standard:

    https://tools.ietf.org/html/draft-thomas-crypto-conditions-04

Hush will enable the following CryptoConditions initially, and plans to enable
others as time goes on:

\begin{itemize}
    \item Heir - cryptocoin inheritance
    \item Gateway
    \item Oracle
    \item Channel
    \item Faucet
\end{itemize}

These features will allow for an entire ecosystem of decentralized applications
(dApps) to be built on top of HUSH, which integrate with HushList protocol as
well as cross-chain integrations with other Komodo asset chains, such as BTCH,
ARRR or various others.

\nsection{Hush v1-v2 Total Supply Bug}

\begin{quote}
To save one from a mistake is a gift of paradise.
    - Stilgar to Lady Jessica
\end{quote}

The original Hush devs added the original pre-mine in such a way that Hush would
have a supply greater than the intended 21,000,000 after about 30 years. This
fact was discovered in the process of emulating the current Hush supply curve
(halving interval) on our new Komodo-based chain. This bug will be corrected on
our new chain (Hush v3) by ceasing block rewards when total supply hits 21M
coins, as intended.

As a reminder, NONE of the current Hush team received any the original 0.76\%
(160,000 HUSH) pre-mine. All of the original Hush developers who received the
reward have long since left the project.

The current Hush chain (version 2) will attain a supply of 21,000,000 coins at
Block 5922239 which will have a Block Reward of 0.09765625 HUSH. This happens
between the 7th and 8th halvings.

But because the original devs of Hush added a pre-mine of 160,000 HUSH in blocks
1 through 4, the current Hush supply curve will continue past the 21M supply
mark until Block 26039999 when supply is 21159937.4895 HUSH and the last block
reward of 1 satoshi is awarded just before the 31st halving.

The core issue is that blocks 1 through 4 had a block reward of 40,000 each
instead of 12.5 each in the GetBlockSubsidy() function defined in main.cpp, but
the overall emission schedule was not modified to take this into account.

This mistake would eventually lead to an extra 159,937.4895 HUSH of total supply
beyond the intended totaly supply of 21M, which would happen after about 30
years, between the 7th and 8th halvings.

This bug in the supply curve of Hush will be fixed during the migration to a
Komodo asset chain, where we can use ac\_end=N to specify a block when block
rewards should cease. This will allow us to enforce the intended 21M total
supply of Hush.

To calculate the value of ac\_end for the new Hush chain:

ac\_end = 5922239 - (number of blocks in old Hush chain) - (zero block reward transition period)
ac\_end = 5922239 - 500000 - 128
ac\_end = 5422111

TODO: deal with asset magic epsilon, which could be up to 10? blocks of BR
average case it will be 5 blocks, worst case 10, so 5422101 would enforce just less than 21M

To clarify, Hush will have a consensus rule that block rewards stop at block
5422111 which will enforce a total supply of 21M coins.

\nsection{New Blockchain Size}

The Hush blockchain will essentially be compressed, down from its current size
of about 3.4GB to a few megabytes. This is related to the fact that there are
about 30,000 unique addresses on the Hush blockchain which contain funds.

This compression will greatly improve the user experience of new Hush users,
which can install and sync a full node in just a few minutes.

\nsection{Delayed Proof-Of-Work}

\begin{quote}
    May thy knife chip and shatter.
        - Fremen saying of ill will against an adversary
\end{quote}

HUSH will continue to have Delayed Proof-of-Work as protection against 51\%
attacks and double spend attack prevention. No other technology is proven
in production like DPoW.

The current implementation of DPoW in Hush v2 was tested in a test attack.  A
large amount of hashrate was rented at NiceHash, and a 51\% attack was
attempted, which would re-organized a notarized block. The attack repeatedly
failed and wasted a large amount of BTC of the simulated attacker.

HUSHv3 will be migrating to the core DPoW implementation of Komodo itself,
instead of relying on the implementation that was ported from Komodo to the
Hush v2 codebase. This further increases HUSH development velocity and reduces
our maintenance burden to merge upstream code.

\nsection{Cryptopia Attack}

\nsection{Special Thanks}

Special thanks to jl777 and the greater Komodo community for inspiring a new
generation of cypherpunks to innovate outside the constraints of Bitcoin and
Zcash core communities.

Special thanks to radix42, Savior Of The Memo Field, for mentoring me in my
early days as a cryptocoin dev.

\nsection{References}

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\end{document}