Tiny Crypto

A minimal blockchain-based cryptocurrency built entirely for learning purposes in Rust. It is roughly modeled after a extremely simplified Bitcoin, focusing on foundational blockchain elements to create a small and functional digital currency.

Development

Install Rust

Tech stack: Standard crypto crates (secp256k1, sha2, ripemd, bincode, rs_merkle).

Testing

cargo test

Architecture

The codebase follows a bottom-up layered design:

Primitives

• crypto.rs — Core cryptographic building blocks: SHA-256d hashing, secp256k1 keypair generation/signing/verification, Bitcoin-style Base58Check addresses (SHA-256 + RIPEMD-160), and Merkle trees.
• constants.rs — Protocol parameters: 50-coin genesis reward, 210k-block halving interval, 1000 block size limit.

Transactions

• transaction.rs — UTXO-based transaction model. Each transaction has a single input (either a coinbase for mining rewards, or a reference to a previous output) and multiple outputs. Transactions are signed with ECDSA and identified by their double-SHA-256 hash.

Blocks

• block.rs — Block structure with header (prev hash, merkle root, timestamp, difficulty, nonce). Implements naive proof-of-work mining and validation (hash meets difficulty target, merkle root matches, coinbase reward is correct, no duplicate txs, signatures valid).

Chain Management

• utxo_set.rs — Tracks unspent transaction outputs. Validates that inputs reference real UTXOs, are signed by the output owner, and output values match.
• chain.rs — Linked list of BlockchainNodes with cumulative work calculation (for heaviest-chain selection). Can rebuild the UTXO set from the full chain.
• block_manager.rs — Stores blocks/nodes by hash. Handles orphan blocks (blocks whose parent hasn't arrived yet).
• mem_pool.rs — Holds pending transactions validated against a projected UTXO set.

Node State

• node.rs — Ties everything together. NodeState handles incoming blocks (validate, store, reorg if heavier chain) and transactions (validate, add to mempool). Node wraps state with a keypair and can create/mine new blocks from the mempool.

Network

• Planned Peer to peer networking (with libp2p)

CLI

• (main.rs)
• Planned Subcommands for interaction with the node/chain (viewing chain state, submitting transactions)

Key Design Decisions / Simplifications

• Single input per transaction — simplified vs. Bitcoin's multi-input model
• UTXO rebuild on reorg — the entire UTXO set is rebuilt from scratch when the active chain tip changes
• Signing/Scripting P2PKH only, no dynamic scripting functionality supported.