MultiChain Developer Q&A - Recent questions tagged spv

Missing exactly one transaction after "merkleblock"-message

Mon, 04 May 2020 17:30:01 +0000

Hi,

I've come across an "issue" where after a "merkleblock"-message Multichain leaves out exactly one of transactions in the following "tx"-messages. I'm not sure whether this is intended behavior and I just misunderstood the Bitcoin documentation or an actual problem.

Here's the setup:
I'm using Multichain as a single full node in combination with a browser based Bitcoin SPV node (bcoin).
When the SPV node creates and announces a new unconfirmed transaction Multichain receives, validates and adds it to the next block as expected. Multichain proceeds to announce the new block ("inv"-message) and the SPV node requests it ("getdata"-message) as should be. In response, Multichain sends a "merkleblock"-message to the SPV node as well as separate "tx"-messages for all but one transaction of the newly created block.

From the Bitcoin documentation [1]:
The merkleblock message is a reply to a getdata message which requested a block using the inventory type MSG_MERKLEBLOCK. It is only part of the reply: if any matching transactions are found, they will be sent separately as tx messages.

And from [2]:
After a merkleblock, transactions matching the bloom filter are automatically sent in tx messages.

Since I didn't set a bloom filter I expected one "tx"-message for every transaction that is included in the block. However, Multichain leaves out exactly one of those transactions.
I've noticed that the missing transaction is always the one the SPV node announced earlier. My best guess here is that Multichain assumes the SPV node won't need that transaction a second time since it announced it in the first place? Is this intended behavior by Multichain or am I missing something here?

Thanks in advance and best regards

[1] https://bitcoin.org/en/developer-reference#merkleblock
[2] https://en.bitcoin.it/wiki/Protocol_documentation#filterload.2C_filteradd.2C_filterclear.2C_merkleblock

Connect Android SPV Bitcoin Wallet with permissioned Multichain blockchain

Thu, 17 Aug 2017 09:51:44 +0000

Hi all,

I need to connect an Android SPV Wallet (e.g. this one) with a Multichain private permissioned blockchain. The application requirements are that permissions and streams of the Multichain blockchain should be leveraged, while we don't need the assets feature. I found that one should change these blockchain parameters so as to use a permissioned Multichain blockchain with a mobile wallet instead of a Bitcoin chain.

Some relevant questions:

Are these the only changes to be done to make it work?
Is there any step-by-step guide to achieve the connection flawlessly?
Would you suggest another Android SPV Wallet? e.g. can this forked library work fine with Android mobile devices? (I plan to install and test the wallet on an android tablet, and then on an android smartphone).

Many thanks in advance for your responses!

Regards,

Natassa

SPV wallets support for assets created on multichain?

Mon, 03 Oct 2016 10:14:05 +0000

Hi Multichain Team,

Do the 2 wallets mentioned on the developers page http://www.multichain.com/developers/ support native assets created by users on the chain?

Also will they support permissions like a full node supports?

SPV node

Mon, 26 Sep 2016 11:23:49 +0000

Hi Multichain Team,

Is it possible to create a SPV node using multichain style addressing, I mean without tweaking it to use bitcoin compatible addresssing?

Or if I am using aplha 24 version of multichain, how do I create a SPV node?

Options for Multichain SPV client

Thu, 02 Jun 2016 11:32:32 +0000

Hello MultiChain.

In an scenario with a MultiChain network and thousand of potential users I was thinking in generating the users' addresses in a MultiChain node and operate with them using the RPC API from a very lightweight mobile client, but, if I understood well, in this case all the private keys of the users will be in the MultiChain node. Now, I am thinking in the development of an SPV wallet for the users and I would like to know which are the alternatives to do this.

I have read about BitcoinJ for Multichain, that should work if the MultiChain network behaves like the Bitcoin network, but I have a doubt here: does BitcoinJ for Multichain support the custom issued assets and the permission management that Multichan includes?

Apart from BitcoinJ, do you know about other alternatives to implement a Multichain wallet for mobile phones that avoids the storage of the private keys in a network node?

Thanks in advance.

Regards.

SPV node

Fri, 01 Apr 2016 05:51:58 +0000

Hi,

Is it possible to start a SPV node in multichain like bitcoin provides?

Connect several users

Sun, 07 Feb 2016 07:41:06 +0000

What's the most secure way of having several users in a node?
The node being a hot wallet for all is not a good idea.
Ideally, each one has a spv wallet, but a web wallet is an option, I guess?