cmc/cleberg.net
My personal web garden & blog.
clone: git clone https://gitbay.org/cmc/cleberg.net.git
99575d28c574803e78084ac5ce0eb499e0e8fdce
unsigned
author: Christian Cleberg <hello@cleberg.net> · 2025-07-07T14:30:34Z
build.py | 15 +- content/blog/2025-06-27-how-blockchain-works.org | 197 +++++++++++++++++++++++ 2 files changed, 211 insertions(+), 1 deletion(-) @@ -115,6 +115,7 @@ def get_recent_posts_html(content_dir="./content/blog", num_posts=3): "date": re.compile(r"^#\+date:\s*<(\d{4}-\d{2}-\d{2})"), "slug": re.compile(r"^#\+slug:\s*(.+)$", re.IGNORECASE), "filetags": re.compile(r"^#\+filetags:\s*(.+)$", re.IGNORECASE), + "draft": re.compile(r"^#\+draft:\s*(.+)$", re.IGNORECASE), } for org_path in Path(content_dir).glob("*.org"): @@ -122,6 +123,7 @@ def get_recent_posts_html(content_dir="./content/blog", num_posts=3): date_str = None slug = None tags = [] + is_draft = False with org_path.open("r", encoding="utf-8") as f: for line in f: @@ -153,17 +155,28 @@ def get_recent_posts_html(content_dir="./content/blog", num_posts=3): tags = [t for t in raw.split(":") if t] continue + m = header_patterns["draft"].match(line) + if m: + draft_value = m.group(1).strip().lower() + if draft_value != "nil": + is_draft = True + break + continue + # Stop scanning once we have all required fields if title and date_str and slug and tags: break + if is_draft: + continue + if title and date_str and slug: try: date_obj = datetime.strptime(date_str, "%Y-%m-%d") except ValueError: # Skip files with invalid date format continue - + posts.append( { "title": title, new file mode 100644 @@ -0,0 +1,197 @@ +#+date: <2025-07-07 Mon 00:00:00> +#+title: Blockchain Series #1: How Blockchain Works Under the Hood: Hashes, Keys, and Signatures Explained +#+description: Dive into blockchain's cryptographic foundations. Explore how hash functions, Merkle trees, and digital signatures secure distributed, tamper-resistant ledgers. +#+slug: how-blockchain-works +#+filetags: :blockchain:encryption: +#+draft: t + +/This is Part 1 of a series I'm writing on blockchain. Stay tuned for further +editions./ + +Blockchain is one of those technologies that seems to generate more marketing +buzz than real understanding. Everywhere you look, people talk about +decentralization, trustless systems, and the next big disruption. But beneath +the hype, blockchain systems rely on well-understood cryptographic building +blocks to do something very specific: maintain a secure, tamper-resistant ledger +without needing a central authority. + +If you're serious about understanding blockchain, it's critical to understand +the cryptographic primitives that make it work. Hash functions, digital +signatures, and public-key cryptography aren't just jargon—they're the core +mechanisms that let a distributed network agree on a shared history no one can +easily rewrite. + +This post is Part 1 of a multi-part series on blockchain. Here, we'll focus on +these fundamental building blocks—how they work, why they're used, and how they +fit together to provide the security and trust that blockchain promises. + +* What is Blockchain? + +At its core, a blockchain is a distributed, append-only ledger shared among +participants in a network. + +What does this mean? Essentially, we can think of a standard, non-technical +ledger (book of accounts where transactions are recorded against accounts). When +introductin the idea of a blockchain, let's extend the idea of a standard ledger +and make a few connections: + +- Each block of transactions is connected cryptographically to the block before + it, via a [[https://en.wikipedia.org/wiki/Cryptographic_hash_function][cryptographic hash]]. This is what forms a =chain= of blocks, or + records. +- Each block consists of: + - A list of validated transactions + - A timestamp + - A cryptographic hash of the previous block (ensuring immutability) +- Each transaction within a block is initiated between addresses, signed with + cryptographic keys, and sent to the blockchain for validation (e.g., + proof-of-work, proof-of-staking, etc.). +- The blockchain is shared amongst nodes in the network, who agree on the state + of the blockchain through consensus mechanisms. + +As we can see, the decentralized nature and cryptographic linking of +transactions and blocks ensures that modifying the history is infeasible. + +If you're more of a visual person, here's a very basic diagram of a standard +blockchain structure. + +#+begin_example ++------------+ +------------+ +------------+ +| Block 1 | -> | Block 2 | -> | Block 3 | +|------------| |------------| |------------| +| Data | | Data | | Data | +| Prev Hash: | | Prev Hash: | | Prev Hash: | +| 00000000 | | <hash1> | | <hash2> | +| Hash: | | Hash: | | Hash: | +| <hash1> | | <hash2> | | <hash3> | ++------------+ +------------+ +------------+ +#+end_example + +* What Problems is Blockchain Trying to Solve? + +I will be diving into the technical details of blockchains later in this post, +but what exactly is the reason blockchain exists? + +You may know of cryptocurrencies, such as Bitcoin, but that is only one of many +use cases for blockchains. + +As we learned in the section above, a blockchain can be equated to a ledger. +With this in mind, let's dive into a few interesting use cases: + +** Immutable record-keeping + +If you simply need a ledger that cannot be modified easily and can establish a +decentralized network to support that, blockchain is a great technology. + +** Trust without central authority + +The use of a decentralized system means that we do not need to rely on a +centralized authority (e.g., Social Security, a bank, etc.) to store and provide +access to information you need to record. + +Think of the US Social Security Number (SSN) system. Each time you want to +perform actions that require verifying your identify (e.g., opening bank +accounts, investment accounts, child birth, etc.), you are currently required to +provide your SSN. + +However, this is a singular number - which means that if someone learns it, they +can (essentially) now act as you. + +Now imagine a scenario where the SSN system is a blockchain where you have both +your private key for providing evidence to people that you are you. For example, +you open a bank account and sign your form with your private key. Now, the bank +can take that and use your public key to decrypt the message and verify that you +are you, without needing to know your private key. + +Another scenario is that, during a background check, a company could use your +public key and consult the related blockchain to validate specific pieces of +information. For example, if your identity alone is in one block, you could +provide that information to your employer without providing your full SSN and +all related personal information for as long as they keep your SSN on file. + +** Double-spending problem + +With the introduction of digital assets, such as cryptocurrencies and +non-fungible tokens, a new risk is introduced: without control, these assets +could be copied and reused at-will. + +To solve this problem, digital assets are transacted on a blockchain to ensure +that the decentralized system of nodes provide consensus on validating +transactions, transactions are recorded in a transparent and tamper-resistant +manner, and cryptographic functions are performed to order the transactions +logically on chain. + +* The Role of Cryptography in Blockchain +- Why cryptography matters +- Confidentiality vs. integrity/authenticity +- Core goals: + - Tamper-evidence + - Secure identification + - Non-repudiation + +* Hash Functions +- What is a cryptographic hash? +- Properties: + - Collision resistance + - Pre-image resistance +- How blockchain uses hashes: + - Chaining blocks together + - Block headers + - Transactions +- Example command: + #+begin_src bash + echo -n "Hello, Blockchain" | sha256sum + #+end_src +- Optional diagram: chain of blocks with hashes + +* Merkle Trees +- Summarizing many transactions in a single root hash +- Use case: efficient inclusion proofs +- Example diagram (ASCII art if desired) +- Why Merkle roots are in block headers + +* Public Key Cryptography +- Quick refresher +- Public/private keypairs +- Addresses derived from public keys +- Importance of keeping private keys secret + +* Digital Signatures +- Purpose: proving authorship without revealing private key +- Mention ECDSA / EdDSA +- How transactions are signed +- Example snippet: + #+begin_example + Alice signs transaction with her private key + → Anyone can verify with her public key + #+end_example +- Why signatures prevent forgery + +* Bringing it All Together: Blockchain Data Structures +- Block structure: + - Block header with previous block's hash + - Merkle root + - Timestamp, nonce +- How the chain ensures immutability +- Example flow: + 1. User creates a transaction + 2. Signs it + 3. Transaction included in block + 4. Block hash links to previous block + +* Proof of Work (Optional) +- Hash puzzles to add blocks +- Why it's hard to modify history +- Keep this section simple + +* Conclusion +- Summarize how these primitives work together +- Tease next post: "Next, we'll explore security threats and how blockchain + networks mitigate them." +- Optional links to further reading: + - Bitcoin whitepaper + - Ethereum docs + - Cryptography references + +* Optional Extras +- Glossary box with terms (hash, signature, Merkle tree) +- External references (e.g., NIST docs on hashes)