How is GreenAddress handling the BIP91/BIP148 soft fork?

BIP91 (see https://github.com/bitcoin/bips/blob/master/bip-0091.mediawiki) has now been activated by a large majority of miners. This means that miners are now signaling to activate Segregated Witness (also known as segwit or BIP141, see https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki).

If BIP91 is enforced by a majority of miners as expected, they will ignore blocks that are not signaling segwit. This will have the effect of activating Segregated Witness on the main Bitcoin chain.

In order to ensure that the service is not affected by any miners that do not enforce BIP91, we are now enforcing BIP91 on our service nodes. This means we are only considering blocks that signal segwit as valid. This aligns the service with the majority of miners and prevents us from processing blocks that are likely to be orphaned/reorganized out of the blockchain. This in turn should prevent our users from being misled or confused by transactions and/or confirmations that would later disappear.



Enforcing BIP91 in this manner is compatible with the User Activated Soft Fork (i.e. UASF, also known as BIP148, see https://github.com/bitcoin/bips/blob/master/bip-0148.mediawiki). As things currently stand we do not foresee any issues or long lasting split arising from BIP148 activating on August 1st.

Users of our Android app GreenBits can configure it to point to their own node to independently verify validity of confirmations.

Will GreenAddress support a hard fork? How can I spend coins on a hard fork chain?

As of today there hasn’t been any hard fork proposal that has gathered consensus. A hardfork is something that anyone can do at any time and it is infeasible for companies and developers to have reasonable support for proposals that are contentious. We do not currently plan to support a specific hard fork at this time.

If you wish to be able to spend coins on a chain that clones the Bitcoin ledger, we advise that you move your coins from GreenAddress to a wallet that will allow you to split your coins safely. Coins that are held in GreenAddress may not be able to be split, and transactions that occur on GreenAddress may be replayed on the forked chain. If you do not care about forked chains, or you believe a given fork will not last, then you can simply ignore the hard fork. Your coins on the main Bitcoin chain will remain valid and spendable there as usual.



Please note that we cannot provide support services for users who wish to split coins outside of GreenAddress, and we do not plan to develop split support for coins in GreenAddress wallets even if the forked chain coins should survive or rise in value.

We have a position statement on contentious forks which you can read at https://blog.greenaddress.it/2017/03/27/greenaddress-position-on-contentious-forks/.

What about Bitcoin Cash/Bitcoin ABC/Segwit2X support?

See the above question on hard fork support.

What about normal Segwit support? Can I create segwit transactions once it activates?

We support segwit and will enable this functionality as an opt-out option for users after it is fully activated and our testing of the features is complete. We will announce this before we enable the functionality along with instructions on how to opt-out if you wish. If you would like to test segwit integration or how our wallets work with segwit, you can use our testnet service which is already segwit enabled.

As always, if you have any questions, please feel free to contact us at info@greenaddress.it

Lawrence Nahum

GreenAddress Lead

Senior Architect @ Blockstream