Yasho 夜晶 Whitepaper

A Proof of Work cryptocurrency designed for the gaming community.

1. Abstract

Yasho (YSO) is an open-source Proof of Work cryptocurrency built initially for the gaming community, with the long-term vision of becoming a universal digital currency for online purchases. Yasho enables gamers to mine cryptocurrency using their existing GPU hardware during idle periods and spend the earned tokens within gaming ecosystems — and eventually, anywhere online.

This paper describes the technical architecture, consensus mechanism, economic model, and design philosophy behind Yasho. The protocol is built on proven cryptographic principles — Double SHA-256 hashing, ECDSA digital signatures, and the UTXO transaction model — while introducing a balanced difficulty adjustment mechanism that prevents mining centralization and preserves accessibility for individual miners.

2. Introduction

The gaming industry generates hundreds of billions of dollars in annual revenue, yet gamers remain primarily consumers in the digital economy. Millions of gaming PCs equipped with powerful GPUs sit idle for hours every day — after gaming sessions, overnight, or during work hours.

Yasho bridges this gap by providing a cryptocurrency that:

• Leverages existing gaming hardware (GPUs) for mining
• Maintains fair mining conditions that favor individual miners over industrial operations
• Provides a native digital currency for gaming economies
• Operates on a fully decentralized peer-to-peer network

While Yasho starts in the gaming world, the long-term vision extends far beyond. As the network grows and adoption increases, YSO is designed to evolve into a universal digital currency — usable for any online purchase, not just gaming. The gaming community is the launchpad; the destination is a currency for everyone.

3. Problem Statement

Existing cryptocurrencies face several challenges that make them unsuitable for the gaming community:

3.1 Mining Centralization

Bitcoin and similar SHA-256 coins have seen mining become dominated by large-scale industrial operations with specialized ASIC hardware. Individual miners with consumer GPUs cannot compete, eliminating the decentralization ethos that made cryptocurrency appealing.

3.2 No Gaming Integration

Major cryptocurrencies are designed as general-purpose financial instruments. There is no native connection between mining cryptocurrency and the gaming ecosystem where many potential miners already operate.

3.3 Complexity

Running a full cryptocurrency node typically requires technical expertise, separate wallet software, and complex configuration. This creates a barrier for gamers who want to participate but lack blockchain experience.

4. The Yasho Solution

Yasho addresses these challenges through three key design principles:

4.1 GPU-Friendly Mining

Yasho uses Double SHA-256 Proof of Work, which runs efficiently on GPUs via OpenCL acceleration. The difficulty adjustment algorithm (Section 6) includes safeguards that prevent any single entity from gaining disproportionate control of the network hashrate. The difficulty change per adjustment period is clamped within a 4x time ratio range, ensuring gradual transitions that individual miners can adapt to.

4.2 All-in-One Node

The Yasho binary is a single executable that bundles everything a user needs:

• A full blockchain node
• A built-in miner
• A wallet manager
• A REST API
• A web interface with block explorer, wallet dashboard, and documentation

Running yasho --mine --api 8080 starts the entire system. No additional software, no external dependencies.

4.3 Gaming-First, Then Everywhere

YSO tokens are initially designed to circulate within gaming communities — enabling peer-to-peer trades of in-game items, cosmetics, and services. The low barrier to entry ensures that any gamer with a GPU can participate as both a miner and a spender.

But Yasho's ambition doesn't stop at gaming. As adoption grows, YSO is designed to become a universal digital currency for online purchases — from digital goods and subscriptions to everyday e-commerce. The gaming community provides the critical mass of early adopters; from there, Yasho expands into a currency for everyone.

5. Consensus Mechanism

Yasho uses Nakamoto consensus with Double SHA-256 Proof of Work. The longest valid chain is considered the canonical chain.

5.1 Block Structure

Each block in the Yasho blockchain contains:

• Timestamp — Unix timestamp of block creation (validated against median of last 11 blocks)
• Transactions — List of validated transactions (max 1,000 per block)
• PrevBlockHash — Double SHA-256 hash of the previous block
• Hash — Double SHA-256 hash of this block's header
• Nonce — Value iterated during mining to find a valid hash
• Height — Position in the chain (0 for genesis)
• Difficulty — Number of leading zero bits required in the hash
• MerkleRoot — Root hash of the Merkle tree of all transaction IDs (computed using Double SHA-256)

5.2 Mining Process

Mining consists of finding a nonce such that the Double SHA-256 hash of the block header is numerically less than a target value derived from the current difficulty. Double SHA-256 means the data is hashed twice: SHA-256(SHA-256(data)). The target is calculated as:

The miner increments the nonce and hashes the block header (previous hash + Merkle root + timestamp + difficulty + nonce) until a valid hash is found. Mining supports both multi-core CPU parallel processing and GPU acceleration via OpenCL (currently on Windows). A higher difficulty requires more leading zero bits, exponentially increasing the computational work required.

5.3 Block Validation

A block is valid if and only if:

1. The Double SHA-256 hash of its header data (with the stored nonce) matches the stored hash
2. The hash is numerically below the target for its stated difficulty
3. The PrevBlockHash matches the hash of the preceding block
4. The block's timestamp is valid (not before the median of the last 11 blocks, not more than 2 hours in the future)
5. All transactions have valid ECDSA signatures
6. No double-spending of UTXOs occurs within the block
7. The coinbase reward does not exceed the block reward plus transaction fees
8. Coinbase outputs cannot be spent until 100 blocks have been mined on top (coinbase maturity)

6. Difficulty Adjustment

Yasho adjusts mining difficulty every 10 blocks to target a block time of 10 minutes (600 seconds). This frequent adjustment window allows the network to respond quickly to changes in hashrate.

6.1 Algorithm

At every 10th block, the algorithm compares the actual time taken to mine the last 10 blocks against the expected time (6,000 seconds):

The difficulty is adjusted using a multi-level system based on how far the actual mining speed deviates from the target:

• If ratio < 0.25 (blocks mining 4x too fast): difficulty increases by 2
• If ratio < 0.5 (blocks mining 2x too fast): difficulty increases by 1
• If ratio > 4.0 (blocks mining 4x too slow): difficulty decreases by 3
• If ratio > 2.0 (blocks mining 2x too slow): difficulty decreases by 2
• If ratio > 1.5 (blocks mining 1.5x too slow): difficulty decreases by 1
• Otherwise: difficulty remains unchanged

This multi-level approach allows the network to react faster to large hashrate changes while maintaining stability during normal operation. A minimum difficulty of 8 is enforced to prevent the network from becoming trivially easy to mine.

6.2 Anti-Monopoly Clamping

To prevent extreme difficulty swings — which could allow a mining farm to suddenly dominate the network or exclude smaller miners — the actual time is clamped before evaluation:

This means the time ratio used for the decision is bounded to a 4x range, and the difficulty can change by at most 2 levels up or 3 levels down per adjustment period. Even if a massive mining farm joins or leaves the network, the difficulty adjusts gradually, giving individual miners time to adapt.

6.3 Adaptive Difficulty

Yasho's difficulty is fully adaptive and depends on the network's total hashrate and mining speed. There is no fixed starting value — the protocol continuously adjusts difficulty based on how fast blocks are being produced relative to the 10-minute target. When more miners join and hashrate increases, difficulty rises to maintain the target block time. When miners leave, difficulty decreases to ensure blocks continue to be produced at a steady rate. This self-regulating mechanism ensures that Yasho remains mineable regardless of network size, from a single node to a global mining network.

7. Transaction Model

Yasho uses the Unspent Transaction Output (UTXO) model, the same model used by Bitcoin. This provides strong security guarantees and straightforward verification.

7.1 UTXO Concept

Instead of maintaining account balances, the blockchain tracks individual transaction outputs. Each output specifies an amount and a recipient (identified by their public key hash). To spend funds, a user references previous unspent outputs as inputs and creates new outputs.

7.2 Transaction Structure

• Inputs — Each input references a previous transaction output (by transaction ID and output index) and includes an ECDSA signature proving ownership
• Outputs — Each output specifies an amount (in YSO) and a recipient address
• Change — If inputs exceed the intended transfer amount, a change output is created back to the sender

7.3 Coinbase Transactions

Each block's first transaction is a coinbase transaction — a special transaction with no inputs that mints new YSO as the block reward, paid to the miner's address.

7.4 Transaction ID

Each transaction's ID is computed as the Double SHA-256 hash of its serialized inputs and outputs, ensuring uniqueness and integrity.

8. Wallet System

8.1 Key Generation

Yasho wallets use ECDSA with the P-256 (secp256r1) elliptic curve. Each wallet consists of:

• A private key — a 256-bit random number on the P-256 curve
• A public key — the corresponding point on the curve (uncompressed, 65 bytes)
• An address — derived from the SHA-256 hash of the public key
• A seed — a 32-byte hex string for wallet recovery

8.2 Transaction Signing

When spending funds, the wallet signs each input using ECDSA. The signed data consists of the referenced transaction ID concatenated with the output index. Any node can verify the signature using the sender's public key.

8.3 Encryption & Storage

Wallet data is persisted locally in wallets.dat within the node's data directory. Wallets can be encrypted at rest using AES-256-GCM encryption with a password-derived key (via the scrypt key derivation function). When encryption is enabled, the wallet file is fully encrypted and requires the password at startup to unlock. This file must be backed up to prevent permanent loss of funds.

9. Network Architecture

9.1 Peer-to-Peer Protocol

Yasho nodes communicate over TCP using JSON-encoded messages with optional TLS 1.3 encryption. Each message is prefixed with a network magic identifier (yasho-mainnet-v1) to prevent cross-network contamination. The P2P layer handles:

• Peer discovery — Nodes connect to known peers and exchange peer lists (max 50 peers)
• Block propagation — Newly mined blocks are broadcast to all connected peers
• Transaction broadcasting — Pending transactions are shared across the network
• Chain synchronization — New nodes download and verify the full chain from peers
• Orphan block handling — Blocks received out of order are stored (up to 100) and automatically applied when the chain catches up
• Keepalive — Ping/pong messages every 30 seconds to detect disconnected peers

9.2 Network Security

The P2P layer includes multiple protections against malicious peers:

• TLS 1.3 — Optional encrypted connections using auto-generated ECDSA P-256 certificates
• Ban system — Peers accumulate a ban score for protocol violations. When the score reaches the threshold (100), the peer is banned for 24 hours
• Per-IP connection limit — Maximum 3 connections per IP address to prevent Sybil attacks
• Message size limit — Messages are capped at 10 MB to prevent memory exhaustion

9.3 API Layer

Each node exposes a RESTful HTTP API with two tiers of access. The API binds to localhost by default and supports CORS restrictions for web access. All endpoints are rate-limited (60 requests per minute per IP, token bucket algorithm). Write operations additionally require API key authentication via Authorization: Bearer header.

Public endpoints (rate-limited only):

Protected endpoints (rate-limited + API key required):

All POST request bodies are limited to 1 MB to prevent abuse.

9.4 Web Interface

The node serves a built-in web interface at its API port, providing a block explorer, wallet manager, and documentation — accessible from any browser at http://localhost:8080.

10. Tokenomics

10.1 Supply Parameters

10.2 Supply Schedule

Yasho follows a halving schedule identical in structure to Bitcoin's:

The reward halves every 210,000 blocks until it reaches zero, creating a hard cap of approximately 21 million YSO. At 10-minute block times, the first halving would occur approximately 4 years after network launch.

10.3 Deflationary Design

The fixed supply and decreasing emission rate create a deflationary monetary policy. As the gaming economy grows and demand for YSO increases, the diminishing supply of new tokens supports long-term value appreciation.

11. Security

11.1 Cryptographic Primitives

• Double SHA-256 — Used for block hashing, transaction IDs, and Merkle tree construction. Hashing twice mitigates length-extension attacks inherent to single SHA-256. Provides 128-bit collision resistance.
• ECDSA P-256 — Used for transaction signing, verification, and TLS certificate generation. Provides 128-bit security level.
• AES-256-GCM — Used for wallet encryption at rest, providing authenticated encryption.
• scrypt — Password-based key derivation for wallet encryption, resistant to GPU and ASIC brute-force attacks.
• TLS 1.3 — Optional encrypted P2P communications with auto-generated certificates.
• Merkle Trees — Compact proof of transaction inclusion in a block, constructed using Double SHA-256.

11.2 Attack Resistance

• Double-spending — Prevented by the UTXO model. Each output can only be spent once; the UTXO set is rebuilt from the chain and verified at every block. The mempool also tracks spent UTXOs to reject double-spend attempts before mining.
• 51% attacks — The difficulty adjustment clamping (max 4x) slows the ability of a sudden hashrate majority to rewrite the chain, giving the network time to react.
• Replay attacks — Each transaction input references a specific UTXO by transaction ID and index, making transactions non-replayable.
• Forgery — All non-coinbase transactions require valid ECDSA signatures that are verified by every node before block acceptance.
• Sybil attacks — Per-IP connection limits (max 3) and the peer ban system reduce the effectiveness of Sybil attacks on the P2P network.
• API abuse — Rate limiting (60 req/min per IP), API key authentication for write operations, and 1 MB request body limits protect the API from abuse and denial-of-service attempts.
• Premature spending — Coinbase maturity requires 100 confirmations before mining rewards can be spent, preventing miners from spending rewards on blocks that may be orphaned.

11.3 Network Security

• Peer banning — Malicious peers that send invalid blocks, invalid transactions, or violate the protocol accumulate a ban score. At 100 points, the peer is banned for 24 hours.
• Timestamp validation — Block timestamps must be greater than the median of the last 11 blocks and no more than 2 hours in the future, preventing timestamp manipulation attacks.
• Mempool expiration — Pending transactions expire after 24 hours, preventing mempool bloat from stale or abandoned transactions.
• Orphan block management — Up to 100 orphan blocks are stored and automatically applied when the chain catches up, preventing memory exhaustion from orphan flooding.

11.4 Wallet Security

Private keys never leave the local machine. The wallets.dat file stores keys locally and can be encrypted with AES-256-GCM using a user-provided password. Wallet restoration is possible via the seed phrase (32-byte hex). Address validation (format, version byte, checksum) is enforced on all transactions to prevent loss of funds to malformed addresses.

12. Roadmap

13. Conclusion

Yasho represents a cryptocurrency born in the gaming community, built to grow into a universal digital currency. By combining proven blockchain technology with a gamer-friendly design philosophy, Yasho enables millions of GPU owners to participate in a decentralized economy — starting with gaming, expanding to everything.

The key differentiators are:

• Accessibility — A single executable bundles everything: node, miner, wallet, and web interface
• Fairness — The clamped difficulty adjustment prevents sudden mining centralization
• Simplicity — No external dependencies, no complex setup, no separate wallet software
• Gaming first, then everywhere — Starts as the currency for gamers, grows into a currency for all online purchases

Yasho — Mine when you're not playing. Spend on what you love.