Relayed contract interactions ("gasless operation")

[oberstet]

Expand all gas consuming (write transactional) SC functions in XBR smart contracts with bytes signature to allow delegated ETH/gas-less operation

[oberstet]

As far as I can see, there are 2 relevant proposal for tokens (aka "gasless token transfers", which is only part of the problem we have to address .. as in, we might want to be able to delegate_all_ write transactions in all XBR contracts):

• ERC865: Pay transfers in tokens instead of gas, in one transaction ethereum/EIPs#865
• Send by Signature (ERC777 extension) - transfer without paying for gas ethereum/EIPs#965

[oberstet]

ideally, whatever token contract we use, that contract would be:

• ERC20 compatible, so users can still use regular wallets (eg metamask) in which case they need ETH on their wallet to pay the gas for the transfer transaction
• additionally the token would allow delegated transfers where only the market maker needs to pay gas, and the user wallet interacts with the MM via WAMP
• for the latter, the gas would be converted into XBR and deducted from the transferred amount to compensate the MM for its service (the delegated transfer)

[oberstet]

Naming: We should probably use relayer / relay instead of delegate / delegate wording

PRO: the word "delegate" is already used in XBR, and seller/buyer delegates are active components (they have private keys themself, and do stuff themself without being directly 1:1 triggered from outside)
CON: it introduces yet another term ("relayer")

[oberstet]

• https://gsn.openzeppelin.com/
• https://docs.openzeppelin.com/contracts/2.x/gsn

[oberstet]

partially landed already:

• XBRNetwork.registerFor: https://github.com/crossbario/xbr-protocol/blob/c416ae5cd7d828232c8cf19d5506cd1862bf8ea0/contracts/XBRNetwork.sol#L134
• XBRMarket.joinMarketFor: https://github.com/crossbario/xbr-protocol/blob/c416ae5cd7d828232c8cf19d5506cd1862bf8ea0/contracts/XBRMarket.sol#L358
• XBRChannel.openChannelFor

The last one depends on #48

[oberstet]

the missing parts ^ are coming via #90

[oberstet]

landed via #90