Anonymous Zether in Javascript

Anonymous Zether solidity contracts developed by J.P. Morgan and implemented in pure Javascript.

Improvements :

1. Whisper protocol

Whisper the balance b on chain by encrypting b using the shared secret.
Idea suggestion by Zhou Zhiyao @zzy96

1.1 Whisper to receiver:

Given:

- balance of transaction
- index of the receiver
- public key of the receiver
- secret of the receiver
- public view key

Computing the proof hiding the balance for receiver

Retrieving the secret balance from the sender

1.2 Whisper to sender:

- index of the sender
- secret of the sender\

Computing the proof hiding the balance for receiver

Retrieving the secret balance from the sender

2. Proving amount and receiver without revealing sender

Proving to someone that the transaction sent amount b to the receiver i without revealing who the sender was.
Idea suggestion by @benediamond

A proof (c,s) is computed as follows:
- balance of transaction
- index of the receiver
- public view key
- cipher text

Prover - generating proof (c, s)
- Claim
Given r such
Choosing a random element k in F_q and
- computing c
- computing s

Verifier - verify proof (c, s)
- computing K_r
- computing Y_r
- equation verification

3. Under development:

1. Paying gas in Zether.

It enables Zether to be used as a native currency to pay the gas in Zether to the miners accepting it as gas.

- miner fee
- amount
- cipher text

- Homomorphically subtract b and gas from the sender
- Homomorphically add b to the receiver
- Homomorphically add 0 to the decoys
- Add gas to the miner. Homomorphically add can be performed as well

References

1. J.P. Morgan codebase of Zether https://github.com/jpmorganchase/anonymous-zether
2. J.P. Morgan - Anonymous Zether Proposal and Tehnical Report https://github.com/jpmorganchase/anonymous-zether/blob/master/docs/AnonZether.pdf
3. J.P. Morgan Additional features on Zether https://github.com/jpmorganchase/anonymous-zether/blob/master/docs/AnonZether.pdf
4. Zether: Towards Privacy in a Smart Contract World https://crypto.stanford.edu/~buenz/papers/zether.pdf

Special thanks

We want to express our gratitude for the implementation and the help offered us over slack and github.

Main contributors

Benjamin Diamond @benediamond

J.P. Morgan @jpmorganchase

Zhou Zhiyao @zzy96 for the Whisper Protocol