SegWit-related Questions

[festus1973]

I'm new to this so please bear with me. I've been using the Insight API as a client (via BlockExplorer and other public sites) for a while now but am hitting a few snags with regard to SegWit support...

(1) Is there any plan to incorporate searching for transactions related to a particular SegWit address, where the address is expressed in bech32 format ?

example: bc1q9x30z7rz52c97jwc2j79w76y7l3ny54nlvd4ew

Performing such queries currently leads to an error.

(2) I failed to send a SegWit-formatted raw transaction through the Insight API. The transaction is formatted properly and I was eventually able to push it through the BlockCypher API, but Insight always yields a message about the transaction having no inputs. Presumably Insight is reading the SegWit marker flag, which is always zero and immediately follows nVersion, treating it as the input count and choking on that. I was surprised because I had always assumed that the API blindly forwarded the raw hex transaction to a node behind the scenes and then echoed back the success or failure message. If the node itself understands the transaction, I figured in theory it should work. What's the issue here? Is Insight attempting to parse and analyze the transaction bytes before forwarding perhaps?

(3) Does Insight API support the use case of pushing a non-SegWit TX (that is, no SegWit inputs) to SegWit addresses? That is, inputs would all be P2PKH and at least one of the outputs would be P2WPKH.

Again, thanks for the help. Dealing with inbound/outbound transactions from customers, some of which will be SegWit formatted, is a pretty big deal for me so I'm just trying to figure out what I can and can't do with this API.

Best,

Festus

[dabura667]

1. No
2. No
3. Yes

Segwit is a change in the way INPUTS are handled. So sending TO segwit whether it is P2SH nested or “native” segwit (the bc1 address) will work.

However, since insight-api does not understand segwit (it uses a super old version of Bitcoin Core) it can only validate segwit transactions when they are in a block. (Meaning insight can not broadcast or receive unconfirmed segwit spending transactions, but it will show the transaction after it has been confirmed in a block.

Satoshilabs has made a fork of insight that works with segwit.

Why Bitpay doesn’t just use those changes is beyond my comprehension.

[dabura667]

https://btc-bitcore1.trezor.io/

This is a version of insight that supports segwit fully.

[festus1973]

@dabura667

Thanks for the response. Unfortunately, I discovered that the answer to #3 is 'no' as well.

I tried pushing a non-segwit transaction (no segwit inputs) that contained two segwit outputs through Insight. It failed. I verified that the transaction was in fact valid by subsequently pushing it through BlockCypher's API.

The error Insight returns when pushing the transaction indicated that it didn't like the ScriptPubKey of the segwit output. The ScriptPubKey structure for a segwit P2WPKH output is very different than that of a P2PKH output and apparently Insight doesn't know how to parse the former.

All in all, it's a disappointing discovery. I really like the Insight API but without SegWit support, it's markedly less useful.

In any case, thanks again for response!

Best,

Festus

[gabegattis]

I think the root of the issue is how segwit style serialization works. The current bitcore-lib that insight is using, does not support parsing transactions in the new serialization format. We have a separate branch of bitcore-lib that does support segwit serialization. Were are already using it in some other projects. When we are happy with that, we will merge it into master and then insight will be able to use it.