Bitcoin Explained - The Technical Side of Bitcoin

In this episode of The Van Wirdum Sjorsnado, hosts Aaron van Wirdum and Sjors Provoost discuss Bitcoin addresses. Every Bitcoin user has probably at one point used Bitcoin addresses, but what are they, exactly? Aaron and Sjors explain that Bitcoin addresses are not part of the Bitcoin protocol. Instead, they are conventions used by Bitcoin (wallet) software to communicate where coins must be spent to: either a public key (P2PK), a public key hash (P2PKH), a script hash (P2SH), a witness public key hash (P2WPKH), or a witness script hash (P2WSH). Addresses also include some meta data about the address type itself. Bitcoin addresses communicate these payment options using their own “numeric systems”, Aaron and Sjors explain. The first version of this was base58, which uses 58 different symbols to represent numbers. Newer address types, bech32 addresses, instead use base32 which uses 32 different symbols to represent numbers. Aaron and Sjors discuss some of the benefits of using Bitcoin addresses in general. and bech32 addresses in specific. In addition, Sjors explains that the first version of bech32 addresses included a (relatively harmless) bug, and how a newer standard for bech32 addresses has fixed this bug.

In this episode of The Van Wirdum Sjorsnado, hosts Aaron van Wirdum and Sjors Provoost are once again joined by Ruben Somsen. This time, they discuss one of Ruben’s own proposals, called Softchains. Softchains are a type of two-way peg sidechains that utilize a new type of consensus mechanism: proof-of-work fraud proofs (or as Sjors prefers to call them, proof-of-work fraud indicators). Using this consensus mechanism, users don’t validate the content of each block, but instead only check the proof of work header, like Simplified Payment Verification (SPV) clients do. But using proof-of-work fraud proofs, users do validate the entire content of blocks any time a blockchain fork occurs. This offers a security model in between full node security and SPV security. Ruben explains that by using proof-of-work fraud proofs for sidechains to create Softchains, Bitcoin full nodes could validate entire sidechains at minimal cost. This new model might be useful for certain types of sidechains, most notably “block size increase” sidechains that do nothing fancy but do offer more transaction capacity. Aaron, Sjors and Ruben also discuss some of the downsides of the Softchain model.

In this episode of The Van Wirdum Sjorsnado, hosts Aaron van Wirdum and Sjors Provoost discuss Replace By Fee (RBF). RBF is a trick that lets unconfirmed transactions be replaced by conflicting transactions that include a higher fee. With RBF, users can essentially bump a transaction fee to incentivize miners to include the transaction in a block. Aaron and Sjors explain three advantages of RBF: the option the “speed up” a transaction (1), which can in turn result in a more effective fee market for block space (2), as well as the potential to make more efficient use of block space by updating transactions to include more recipients (3). The main disadvantage of RBF is that it makes it slightly easier to double spend unconfirmed transactions, which was also at the root of last week’s “double spend” controversy that dominated headlines. Aaron and Sjors discuss some solutions to diminish this risk, including “opt-in RBF” which is currently implemented in Bitcoin Core. Finally, Sjors explains in detail how opt-in RBF works in Bitcoin Core, and which conditions must be met before a transaction is considered replaceable. He also notes some complications with this version of RBF, for example in the context of the Lightning Network.

In this episode of The Van Wirdum Sjorsnado, hosts Aaron van Wirdum and Sjors Provoost discuss Compact Client Side Filtering, also known as Neutrino. Compact Client Side Filtering is a solution to use Bitcoin without needing to download and validate the entire blockchain, and without sacrificing your privacy to someone who operates a full node (and therefore did download and validate the entire blockchain). Downloading and validating the entire Bitcoin blockchain can take a couple of days even on a standard laptop, and much longer on smart phones or other limited-performance computers. This is why many people prefer to use light clients. These aren’t quite as secure as full Bitcoin nodes, but they do require fewer computational resources to operate. Some types of light clients — Simplified Payment Verification (SPV) clients — essentially ask nodes on the Bitcoin network about the particular Bitcoin addresses they are interested in, to check how much funds they own. This is bad for privacy, since the full node operators learns which addresses belong to the SPV user. Compact Client Side Filtering is a newer solution to accomplish similar goals as SPV, but without the loss of privacy. This works, in short, by having full node operators create a cryptographic data-structure that tells the light client user whether a block could have contained activity pertaining to its addresses, so the user can keep track of its funds by downloading only a small subset of all Bitcoin blocks. Aaron and Sjors explain how this works in more detail, and discuss some of the tradeoffs of this solution.

In this episode of “The Van Wirdum Sjorsnado,” hosts Aaron van Wirdum and Sjors Provoost discuss the newly released Bitcoin Core 0.21.0. Bitcoin Core 0.21.0 is the 21st and latest major release of the Bitcoin Core software, the oldest and most important Bitcoin node implementation, which is often also regarded as the reference implementation for the Bitcoin protocol. Follow Aaron van Wirdum @AaronvanW Follow Sjors Provoost @provoost Follow Bitcoin Magazine @BitcoinMagazine

In this episode of “The Van Wirdum Sjorsnado,” hosts Aaron van Wirdum and Sjors Provoost are once again joined by Ruben Somsen. The trio discusses Drivechain, a sidechain project spearheaded by Paul Sztorc.Sidechains are alternative blockchains, where coins are pegged to bitcoin. This should make the sidechain coins interchangeable with bitcoin and therefore carry an equal value. In a way, sidechains let users “move” bitcoin across blockchains, where they are subject to different protocol rules, allowing for greater transaction capacity, more privacy, and other benefits.Aaron, Sjors and Ruben explain that Drivechain consists of two main innovations. The first is blind merged mining, which lets Bitcoin miners secure the drivechain with their existing hash power, but without necessarily needing to validate everything that happens on the sidechain. The second is hashrate escrows, which lets miners “move” coins from the Bitcoin blockchain to the sidechain and back. The hosts also discuss some of the benefits as well as complications with Drivechain, most notably the security implications of letting miners control the pegging out process. They consider the arguments why this process is incentive compatible (in other words: secure) — or why it might not be.

In this episode of The Van Wirdum Sjorsnado, hosts Aaron van Wirdum and Sjors Provoost discuss the basics of the Lightning Network, Bitcoin’s Layer 2 protocol for cheaper, faster and potentially more private transactions.

In this episode of The Van Wirdum Sjorsnado, Aaron and Sjors discuss why it matters that Bitcoin software is open source… and why even open source software doesn't necessarily solve all software-specific trust issues. In theory, the fact that most Bitcoin nodes, wallets and applications are open source should ensure that developers can’t include malicious code in the programs: anyone can inspect the source code for malware. In practice, however, the number of people with enough expertise to do this is limited, while the reliance of some Bitcoin projects on external code libraries (“dependencies”) makes it even harder. Furthermore, even if the open source code is sound, this doesn’t guarantee that the binaries (computer code) really correspond with the open source code. Aaron and Sjors explain how this risk is largely mitigated in Bitcoin through a process called Gitian building, where several Bitcoin Core developers sign the binaries if, and only if, they all produced the exact same binaries from the same source code. This requires special compiler software. Finally, Aaron and Sjors discuss Guix, a relatively new project that goes above and beyond the Gitian process, to minimize the level of trust required to turn source code into binaries — including trust in the compiler itself.  

In this episode of The Van Wirdum Sjorsnado, hosts Aaron van Wirdum and Sjors Provoost discuss RSK’s shift from a federated sidechain model to the project’s new Powpeg solution. RSK is a merge mined Ethereum-like Bitcoin sidechain developed by IOVlabs. Bitcoin users can effectively move their coins to this blockchain that operates more like Ethereum, and move the coins back to the Bitcoin blockchain when they so choose. Some Bitcoin miners utilize their hashpower to mine bocks on the sidechain, and earn some extra transaction fees by doing so.The tricky part of any sidechain is allowing users to securely move their coins between blockchains. This is technically done by locking coins on the Bitcoin blockchain and issuing corresponding coins on the sidechain, and vice versa: locking coins on the sidechain to unlock the coins on the Bitcoin blockchain.So far, RSK did this by locking the coins into a multi-signature address, for which the private keys were controlled by a group of well-known companies. A majority of them was needed to unlock the coins, which they were to only do if and when the corresponding sidechain coins were locked.RSK is now switching to a Powpeg model where the keys to the multi-signature address are controlled by special tamper-proof hardware modules that are in turn programmed to only unlock coins on the Bitcoin blockchain if and when the corresponding coins on the sidechain are locked, and the transactions to lock these coins up have a significant number of confirmations.Aaron and Sjors explain how this works exactly, and discuss some of Powpeg’s security tradeoffs.

In this episode of The Van Wirdum Sjorsnado, hosts Aaron van Wirdum and Sjors Provoost discussed Bitcoin mempools, Child Pays For Parent (CPFP) and package relay. Package relay is the project that Gloria Zhao will work on as part of her Brink fellowship, which was announced earlier this week, and would make the Lightning Network more robust (among other benefits). Mempools are the collections of unconfirmed transactions stored by nodes, from which they forward transactions to peers. Miners usually select the transactions from their mempools that include the highest fees, to include these in the blocks they mine. Mempools can get full, however, at which point transactions that pay the lowest fees are ejected. This is actually a problem in context of CPFP, a trick that lets users speed up low-fee transactions by spending the coins from that transactions in a new transaction with a high fee to compensate. Tricks like these can be particularly important in the context of time-sensitive protocols like the Lightning Network. In this episode, van Wirdum and Provoost explained how package relay could enable CPFP, even in cases where low-fee transactions are dropped from mempools, by bundling transactions into packets. And they explore why this may be easier said than done.