Post your SegWit questions here - open discussion - big week for Bitcoin!

[achow101]

So I'm reading that this Segwit2X forking could expose BTC users to replay attacks (and maybe to other threats via segwit), but it is not clear at what conditions. To effect replay attacks would take a majority of mining power? Or what exactly?

Replay attacks don't require any hash power, or even any person. Replay can happen accidentally. Replay is that a transaction made on one chain is valid on the other, and becomes confirmed on both chains. The only way to have replay protection is to include it as part of the hard fork.

[DreamweaverVCC]

So how do i send a segwit transaction on electrum? 

[cr1776]

So how do i send a segwit transaction on electrum?  

With the current version creating segwit addresses is done via command line and that may be only for test net as of 2.6.  So, it is a question of an update.  ( https://github.com/spesmilo/electrum/blob/master/RELEASE-NOTES )

[hudd]

So how do i send a segwit transaction on electrum? 

Most wallets are ready for Segwit, but due to security reason they didn't let you create Segwit wallets until it is activated. Electrum dev said that new version will be released soon letting you do so:
https://github.com/spesmilo/electrum/issues/2791#issuecomment-324340931

[hudd]

My question: How can I know if one transaction is Segwit transaction or not. As far as I know, not all P2SH addresses are segwit addresses.

[ScripterRon]

My question: How can I know if one transaction is Segwit transaction or not. As far as I know, not all P2SH addresses are segwit addresses.

You can't tell by looking at the transaction output.  Segwit has a specific script format which hashes to match the P2SH value.  So only the owner of the transaction output knows that it is a segwit output (unless you can guess the owner's public key hash and generate the matching P2SH value).  Of course, once the output is spent, you can tell it is a segwith output by looking at the spending input.

There is a BIP for a native segwit address but it hasn't been implemented yet.

[chesegrinder]

is every wallet provider will support this week Segwit? i dont have any update on my wallet.... i use Blockchain and paxful

[bcsuisse]

How long do you guys think it will take before segwit starts having a major effect on the fees?

As far as getting advantages from segwit activation (for example lighting network) could take several months to see actual advantages, so that will be a curious development to watch, as you mentioned, and surely there are better technical folks that could speculate on these matters.

I think T-Rex means the extra blocksize space

Actual Segwit activation happens at block 481824, according to achow101 above. From there on, people can start using 4MB of blocksize, but only if they're sending to a Segwit address. That will happen before the end of this week, I think around Wednsday or Thursday.

So, you can expect Bitcoin service providing companies (exchanges and larger retailers) to roll out the ability to send to Segwit addresses pretty quick, both to use business2-business and customer-2-business. But regular users need to start using Segwit addresses too, and that takes as long as it takes, no one can force people to do it (the old addresses still work just fine). Miners may begin to incentivise this by prioritising Segwit transactions more, but they already prioritise on the basis of transaction size, so any Segwit incentive would have to be over and above the existing fee per kB logic. All that will take between weeks and months to play out, possibly longer for the last P2PKH addresses to finally move to P2WPKH (the Segwit address/script type).

In addition, there's another BIP out there (171 i think?) that adds a new Segwit specific address format (current practice will be to use Segwit via P2SH addresses). This will be a whole extra new Segwit rollout of sorts. Hopefully, it will be tested and finalised for 0.15.1 (but I'm not at all sure on the specifics, that's just my ideal scenario). This will only add weeks and months to the overall switchover period, but bech32 (the name for the tech behind this new format) has alot of advantages.


Lightning? I expect we can see some test channels running quickly after activation of Segwit, but I think the software clients are still in development even now. Anyone know some more?

I think BIP173 is what you are thinking of:
https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki

As far as when, that is still up in the air.

with all the drama again. do you tink the btc price might take a 30% dump like last time again? would be a chance to buy back btc . before it moons

[F8N00]

I just saw that in new transactions there is an option "Fee per weight unit", what this mean?

example : https://blockchain.info/tx/0f65c4bf90414693575266bd8d6521396f8caaed26d0fab3f730a5837dda0900

It says "Fee per weight unit 78.598 sat/WU" and "Weight 900"

[rublix]

How long do you guys think it will take before segwit starts having a major effect on the fees?

As far as getting advantages from segwit activation (for example lighting network) could take several months to see actual advantages, so that will be a curious development to watch, as you mentioned, and surely there are better technical folks that could speculate on these matters.

I think T-Rex means the extra blocksize space

Actual Segwit activation happens at block 481824, according to achow101 above. From there on, people can start using 4MB of blocksize, but only if they're sending to a Segwit address. That will happen before the end of this week, I think around Wednsday or Thursday.

So, you can expect Bitcoin service providing companies (exchanges and larger retailers) to roll out the ability to send to Segwit addresses pretty quick, both to use business2-business and customer-2-business. But regular users need to start using Segwit addresses too, and that takes as long as it takes, no one can force people to do it (the old addresses still work just fine). Miners may begin to incentivise this by prioritising Segwit transactions more, but they already prioritise on the basis of transaction size, so any Segwit incentive would have to be over and above the existing fee per kB logic. All that will take between weeks and months to play out, possibly longer for the last P2PKH addresses to finally move to P2WPKH (the Segwit address/script type).

In addition, there's another BIP out there (171 i think?) that adds a new Segwit specific address format (current practice will be to use Segwit via P2SH addresses). This will be a whole extra new Segwit rollout of sorts. Hopefully, it will be tested and finalised for 0.15.1 (but I'm not at all sure on the specifics, that's just my ideal scenario). This will only add weeks and months to the overall switchover period, but bech32 (the name for the tech behind this new format) has alot of advantages.


Lightning? I expect we can see some test channels running quickly after activation of Segwit, but I think the software clients are still in development even now. Anyone know some more?

I think BIP173 is what you are thinking of:
https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki

As far as when, that is still up in the air.

with all the drama again. do you tink the btc price might take a 30% dump like last time again? would be a chance to buy back btc . before it moons

If there is any type of drop, it'll come right down to support and retest highs accordingly. As it has done many times in the past... The news that floats around just gives reasons for inexperienced people to be fearful and speculate that BTC is going to zero.

[-ck]

I just saw that in new transactions there is an option "Fee per weight unit", what this mean?

example : https://blockchain.info/tx/0f65c4bf90414693575266bd8d6521396f8caaed26d0fab3f730a5837dda0900

It says "Fee per weight unit 78.598 sat/WU" and "Weight 900"

Blocksize has been replaced by blockweight now. The max block weight is 4MB now unlike previously where it was only block size of 1MB. Each classic transaction is worth 4x its size in blockweight but segwit transactions are worth 1x their size. That means you can have 1MB of classic transactions or up to 4MB of segwit transactions.

Block weight corresponds 1:1 with block size for segwit transactions but is 4:1 for classic transactions. This means that the equivalent of 100 satoshi/byte fee per size in fee per weight is 400 satoshi/byte for classic transactions and 100 satoshi/byte for segwit transactions. That doesn't mean you're paying more for classic transactions though; it means you're paying less for segwit transactions.

[nathan_24]

Does the private key in WIF format tell if the address associated is segwit?

Since the same priv key can generate both segwit and non-segwit addresses, when importing a WIF-encoded priv key, should we ask the user if it is segwit or is that information obtained from the wif-encoded key itself?

[David Rabahy]

Um, so, SegWit is active but when will we see evidence of it helping?  Have any SegWit transactions gone through yet?  Will the transaction count per block start going up?

[cr1776]

Um, so, SegWit is active but when will we see evidence of it helping?  Have any SegWit transactions gone through yet?  Will the transaction count per block start going up?

Welcome back to the forum.

Thanks.  Um, any insights into my questions?

SegWit transactions are going through. Not a lot yet:
http://segwit.5gbfree.com/countsegwit

[achow101]

Does the private key in WIF format tell if the address associated is segwit?

Since the same priv key can generate both segwit and non-segwit addresses, when importing a WIF-encoded priv key, should we ask the user if it is segwit or is that information obtained from the wif-encoded key itself?

No, it does not.

Um, so, SegWit is active but when will we see evidence of it helping? 

When more people start using segwit and more segwit transactions have been made.

Have any SegWit transactions gone through yet? 

Yes. There were 6 segwit transactions in the first block after segwit's activation.

Will the transaction count per block start going up?

As more people begin using segwit, it will. We have also already seen at least one block larger than 1 MB.

[OmegaStarScream]

This could be a little bit irrelevant but from these upcoming modifications: Schnorr, MAST, TumbleBit, Lightning network. Which one of them require SegWit to work or to function at its best?

[Salmen]

This could be a little bit irrelevant but from these upcoming modifications: Schnorr, MAST, TumbleBit, Lightning network. Which one of them require SegWit to work or to function at its best?

Schnorr and Lightning Network is required to show its true value of Segwit.

Schnorr minimize the transaction size by combining all signature inputs to an signature that represents these signatures. Another feature of Schnorr is, if the attacker of a spam choose not the Schnorr signature and still use the old signature, then he needs pay higher fees while the other users pays less fees thanks to Schnorr signature.

Summary with the help of this source(s): [1], [2]


The Lightning network is great for users who are willing to send high-volume transactions instantly. For that the users create a secure network within the blockchain. Also in Lightning Network is Litecoin involved, so they both share its resources to transact all unconfirmed transaction.

Summary with the help of this source(s): [3], [4]

[HeroC]

I am running a BIP148 node with segwit from LukeJr's PPA I believe, should I switch back to using core now?

[achow101]

I am running a BIP148 node with segwit from LukeJr's PPA I believe, should I switch back to using core now?

Yes. Both BIP 148 and BIP 91 are irrelevant now.

[polyhedron]

Since the SW is activated, how can a user now send a SW transaction?
E.g., I'm using an Electrum wallet, a BitPie wallet, and have a qt full node, and sometimes I also send from/to an exchange or shapeshift.
That whether a transaction is SW or not, depends on the sending address, receiving address, or both? How can I create a SW transaction to lower the fee?