Update ethereumjs-util to v6

The latest ethereumjs-util release is 6.1.0 and Ganache is still using 5.2.0.

I’m asking for this mainly because of this change that was introduced in 6.0.0:

[BREAKING] Fixed signature to comply with Geth and Parity in toRpcSig() changing v from 0/1 to 27/28, this changes the resulting signature buffer

To protect devs from signature malleability OpenZeppelin has restricted the accepted signatures to those with v in range 27/28, thus Ganache generated signatures are not validating. See https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1622.

[davidmurdoch]

Closed by https://github.com/trufflesuite/ganache-core/pull/445. Major version bump plan to handle the breaking change can be tracked here: https://github.com/trufflesuite/ganache-core/issues/451

[alcuadrado]

I understand that it’s a breaking change, so it should be introduced in your next major release. This behavior has been present for so long that changing it in a minor version will probably break too many things. I’m not 100% sure about this, as most people dealing with signatures already has code in place to somehow normalize them.

In my experience, this has always been a source of frustration when signing using Ganache or previous versions of ethereumjs-util. Until recently, using eth_sign wasn’t that common though, but I believe that with the increased use of meta-transactions much more developers will encounter this problem. For this reason, I think that the sooner this change can be introduced, the better.

As a data point, I just confirmed with @frangio that OpenZeppelin’s signature verification library only accepts 27/28, and it will be used in the Gas Station Network. Keeping 0/1 will lead to complications when testing projects that make use of either of them.