Connect Android SPV Bitcoin Wallet with permissioned Multichain blockchain

Question

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:

1. Are these the only changes to be done to make it work? 
2. Is there any step-by-step guide to achieve the connection flawlessly?
3. 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

 

Answer 1

First, we've updated those instructions to allow the use of more recent MultiChain protocol versions.

I'm afraid we don't yet have concrete step-by-step suggestions on how to do this, beyond what is written on that page. But if you stick to non-asset transactions the wallet should be highly compatible with minimal changes.

In terms of streams, you would need to add functionality to the to read data from the stream. You can use the bloom filtering in the bitcoin p2p protocol to detect patterns of the stream data, which is formatted as written here:

https://www.multichain.com/developers/data-streams/

Comments

Great - thanks for the update!

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Hi,

I tried similar and I think i made good progress (thanks so much for all the help from this thread so far) until the client reports "invalid merkleblock", like so:

---- 8< ----
connecting
10-23 14:33:09.478 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 socket connected
10-23 14:33:09.478 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 sending version
10-23 14:33:09.652 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 got version 70002, useragent:"/Satoshi:0.10.0/"
10-23 14:33:09.653 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 sending verack
10-23 14:33:09.808 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 got verack in 0.330641s
10-23 14:33:09.808 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 handshake completed
10-23 14:33:09.808 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 connected with lastblock: 14349
10-23 14:33:09.819 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 sending filterload
10-23 14:33:09.820 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 calling getblocks with 1 locators: [50f9e518dbd661adf5ee8ae2f9169bbbb364a82bcbcee81526164de8df320000, ]
10-23 14:33:09.820 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 sending getblocks
10-23 14:33:09.820 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 got getaddr
10-23 14:33:09.820 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 sending addr
10-23 14:33:09.820 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 got ping
10-23 14:33:09.820 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 sending pong
10-23 14:33:10.000 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 got inv with 1 item(s)
10-23 14:33:10.001 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 sending getdata
10-23 14:33:10.056 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 got inv with 2 item(s)
10-23 14:33:10.056 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 sending getdata
10-23 14:33:10.234 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 got inv with 500 item(s)
10-23 14:33:10.239 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 sending getdata
10-23 14:33:10.239 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 calling getblocks with 2 locators: [e0f70089603f2b3b966124cc37e65f5820bb0f786361e036285fd99ee03f0000, 68ca777a538ccd7e973e7caae7cd1d66e7136b2cf64dafff8b9f508759c60000]
10-23 14:33:10.240 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 sending getblocks
10-23 14:33:10.387 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 invalid merkleblock: 242e74e61997a80e57ce28763a15db091a3fa5e218356f2dbb1a192383d60000
10-23 14:33:10.388 19506-19963/com.breadwallet I/bread: 10.15.17.11:2897 disconnected
---- 8< ----

I searched quite a bit and could not find anything about "invalid merkleblock".  I think i did set up my checkpoints ok: i took the first block and a later one at height 600:

---- 8< ----
static const struct { uint32_t height; const char *hash; uint32_t timestamp; uint32_t target; } checkpoint_array[] = {
    {      0, "000032dfe84d162615e8cecb2ba864b3bb9b16f9e28aeef5ad61d6db18e5f950", 1508753723, 0x1f00ffff },
    {      600, "000032dfe84d162615e8cecb2ba864b3bb9b16f9e28aeef5ad61d6db18e5f950", 1508759249, 0x1f00ffff }
---- 8< ----

Any ideas?

Thanks!

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Hi Willem, I'm not sure whether this will solve your problem, but since any checkpointed block automatically checkpoints all previous blocks, please try to add to the checkpoint_array ONLY the last block (the one with the max height in your chain) and see how it goes.

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Thanks Natassa, I'll try that now.

Did you ever get this working?  I'm actually having quite a few issues.  This is but one of them.  I also commented out the code that verifies the block height.

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I managed to download the chain in a mobile device in the Android studio emulator. Could you please tell the exact file and lines that you needed to comment out? I assume you refer to the android breadwallet code, don't you?