Symphonious

Living in a state of accord.

Exploring Ethereum: What happens to transactions in non-canonical blocks?

In Ethereum, there are often short forks near the head of the chain because two miners found the PoW solution for new blocks at around the same time. Only one of those chains will ultimately wind up being considered the canonical chain and any blocks from non-canonical chains wind up having no effect on the state. Non-canonical blocks may wind up being added as ommers in future blocks, but everything in this article applies regardless of whether that happens. 

If your transaction winds up in a non-canonical block, is it doomed for all time? Fortunately no. Most likely your transaction will still wind up being added to a block on the canonical chain even though it’s already wound up in a block on a discarded fork.

Firstly, your transaction might have been selected for both the non-canonical block and the block that wound up on the canonical chain. Those two blocks are part of different forks so the transaction may be valid on both. In that case, whichever chain gets picked your transaction is included. However, depending on which other transactions were picked and the effect they had on world state, your transaction may have done completely different things on each fork.

Secondly, it’s possible that a node saw the non-canonical block first and treated it as part of the canonical chain (because it was the best block known to it at the time). In that case, the node will have removed your transaction from the pending transaction pool because it was already processed.  When the block that actually wound up on the canonical chain turns up, the node will perform a chain re-org to switch to this new block and relegate the original block to a fork. If your transaction isn’t in the canonical block, good clients will re-add it to the pending transaction pool so it can be added to a future block.

If your transaction went into a block that was always seen as non-canonical, then it wouldn’t have been removed from the transaction pool in the first place and continues to wait for a chance to get into a canonical block.

Bottom line, getting included in a non-canonical block does your transaction no harm. It will generally hang around until it makes it onto the canonical chain.

Obscuring Presence of Browser Plugins with window.postMessage

There are a number of browser plugins which inject additional JavaScript APIs into the DOM so websites can take advantage of the plugin functionality.  One example of that is MetaMask which “brings Ethereum to your browser”. This allows any website the user visits to detect that the plugin is installed by checking for the presence of those APIs which may aid them in targeting attacks such as the recent spate of phishing attacks against MetaMask users. So there’s a proposal in place to require websites to get specific authorisation from the user before the APIs will be injected.  And since injecting an API to allow the website to request access would defeat the point, it uses window.postMessage:
Dapps MUST request the web3 API by sending a message using window.postMessage API. This message MUST be sent with a payload object containing a type property with a value of “WEB3_API_REQUEST” and an optional id property corresponding to an identifier of a specific wallet provider, such as “METAMASK”.
If the plugin is installed it will prompt the user for access and if granted inject the APIs into the DOM.  If the plugin isn’t installed or if the user refuses access, the website simply receives no response. Clever.

Bitcoin Redux: crypto crime, and how to tackle it | Light Blue Touchpaper

Interesting review of the regulatory landscape around crypto-currencies. There are a lot of echo’s of issues with the over-the-counter nature of most FX trading, albeit with even less enforced regulation and uncertainty.
Bitcoin Redux explains what’s going wrong in the world of cryptocurrencies. The bitcoin exchanges are developing into a shadow banking system, which do not give their customers actual bitcoin but rather display a “balance” and allow them to transact with others. However if Alice sends Bob a bitcoin, and they’re both customers of the same exchange, it just adjusts their balances rather than doing anything on the blockchain. This is an e-money service, according to European law, but is the law enforced? Not where it matters. We’ve been looking at the details.
Source: Bitcoin Redux: crypto crime, and how to tackle it | Light Blue Touchpaper Also interesting to note is that most of the regulation required is already in place and just needs to be enforced. In most cases there isn’t any need for radical rethinking of laws, just apply the current laws about treating consumers fairly and Know-Your-Customer to this new technology.

The Great Bug Hunt – Allen Pike

A fun thing about programming is that most days, you make progress. Maybe you fix some issues, maybe you add a feature, maybe you build towards something bigger. Your code moves ever forward. Until it doesn’t. On occasion, you will hit a Bug. Not a mundane bug, some trifle you can fix in an hour, or even a day. This is a true Bug. One that defies reason. One that evokes a “that’s not possible,” a “how could this even happen?”, or most dreadfully, a “could there be a bug in the compiler?” Hold on kids, we’re going hunting.

Source: The Great Bug Hunt – Allen Pike

Quite an impressive and entertaining bug hunt story really. And the parting words are oh so true:

Whether the Bug is in your code, a 3rd party library, or the thermal expansion of prototype hardware in the morning sun, the only solution is science. And maybe a little whisky.

The sad state of sysadmin in the age of containers

Essentially, the Docker approach boils down to downloading an unsigned binary, running it, and hoping it doesn’t contain any backdoor into your companies network. Feels like downloading Windows shareware in the 90s to me. When will the first docker image appear which contains the Ask toolbar? The first internet worm spreading via flawed docker images?
Source: The sad state of sysadmin in the age of containers There’s certainly some truth to that.  I’m not entirely sure that the compile-from-source approach was actually that much more secure as it was practically impossible to verify the source code anyway. At which point it makes little to no difference if you’re downloading random binaries off the internet or random source code – either way you’re implicitly trusting the source. Verifying signatures for the stuff you download would be a big improvement and many of the newer deployment approaches are very lacking in this area, but it still depends on having a trustworthy way of getting the signature to verify.