FAQ

Some developers have referred to this as an ugly hack, is it accurate?

It was originally thought that segregated witness could only be added to Bitcoin using a hard fork. For that reason, it was considered unlikely to be possible to add to Bitcoin in the near term because hard…

Is SegWit a block size increase?

Yes! Segregated witness replaces the block size limit with a new block weight limit, counting each byte of witness data as 1 unit of weight and UTXO transaction data as 4 units; as a result, the maximum size of a block becomes just under 4 MB.

I heard SegWit was rushed to avoid a hard fork, is that true?

The idea around segregated witness has been in development for nearly two years, and variants of segregated witness have been in production and network testing for over a year. The current soft fork implement is, by all…

Is segregated witness necessary to implement the Lightning Network?

Lightning Network (LN) uses payment channels with Hashed TimeLock Contracts. Both of those things are currently usable on Bitcoin mainnet without segregated witness.

Can miners use the “anyone-can-spend” template to steal users funds?

“Anyone-can-spend” is a misnomer that refers to outputs that look spendable for non-upgraded nodes but really are not.

Does segregated witness create two different fee markets?

No. In fact, it was one of the primary design objective to avoid requiring anyone perform multidimensional optimization because of the problems they create in terms of fee estimation for users and optimal fee block construction…

Why a discount factor of 4? Why not 2 or 8?

Making the discount too large would lead people to use the witness space to store general purpose data on the block chain, or adversarial miners may fill excess space with random junk to defeat fast relay schemes that rely on similar mempools

What incentives do people have to upgrade? P2SH took years to become widely deployed.

Because witness data counts less on the weight of the blocks being created, users that use segregated witness can expect a 75% reduction on fees paid for the witness part of a…

Can un-upgraded nodes be fooled into accepting non-valid segregated witness transactions?

1. Unupgraded full nodes will see the “unknown soft fork” warning after segregated witness activation. They should know they are at risk and upgrade or wait for more confirmations…

So only segregated witness transactions will benefit from the space increase, right?

By being able to use the extra space allocated to witness data, segregated witness transactions will also free up space for legacy transactions which non-upgraded users can leverage.