# The Undercroft (UCFT) ### Whitepaper — Draft v1 --- ## What This Is The Undercroft is an independent, mineable proof-of-work cryptocurrency — its own blockchain, its own miners, its own security, not a token riding on top of someone else's chain. It's built on the same SHA256d proof-of-work that secures Bitcoin, forked from Bitcoin Core itself rather than built from scratch. What makes it different from just being another Bitcoin fork is this: every block you mine has a chance to also mint a real, collectible trading card, on top of the normal coin reward. The coin and the card game aren't two separate things bolted together — the card mechanic is written directly into how blocks get rewarded. ## Why This Exists The Undercroft wasn't built to raise money or chase a hashrate war. It's a passion project that combines two things — mining and collectible card games — built by someone who mines other coins for fun and wanted to see what happens when a coin's appeal comes from something people actually enjoy engaging with, rather than needing constant marketing to stay relevant. That said, "hobby project" doesn't mean "cut corners." The consensus rules, the wallet, and the card mechanic have all been built and tested the same way a serious coin would be — because a coin that shortcuts its own correctness isn't fun for anyone once real money and real collectibles are on the line. ## How Mining Works The Undercroft uses standard SHA256d proof-of-work — the same hashing algorithm as Bitcoin, so existing SHA256 ASIC miners (Bitaxe, Bitdsk, Antminer-class hardware, etc.) can mine it with no special hardware needed, through a pool or your own stratum setup. Block time targets 90 seconds. Difficulty adjusts every single block using Dark Gravity Wave (DGW) retargeting, rather than Bitcoin's every-2016-blocks adjustment — this keeps difficulty tracking the real hashrate actually pointed at the network in near real time, instead of letting it drift for weeks between adjustments. Each block currently pays out 50 UCFT, halving every 350,000 blocks — at target block time, that's roughly once a year. Total supply asymptotically caps at approximately 35,000,000 UCFT, the same geometric halving curve Bitcoin uses, just scaled to this coin's own numbers. ## The Card Mechanic This is the part that doesn't exist in a normal coin. When a block you've mined reaches 30 blocks of depth, there's a chance it also reveals a collectible card. Whether it does — and which one — isn't decided by the block's own hash. It's decided using a commit-reveal scheme: the outcome depends on a hash combining your payout address with both the block's own hash and the hash of a block 30 blocks later, none of which exist yet at the moment you mine. That's deliberate — it means there's no way to mine selectively toward a favorable card outcome, because the information deciding the outcome doesn't exist until long after your block is already locked in. Odds, per mature block: 85% yield coins only, no card. The remaining 15% mint a card — split into uncommon (12%), holo-rare (2.8%), and secret-rare (0.2%). The first set, "The Silicon Strata: 1st Edition," contains 60 original cards with original artwork, no reused or stock art. Future sets are designed to roll out over time without ever requiring a wallet reinstall or update — new sets are fetched and verified automatically. Because the wallet and daemon code are open source, that verification is cryptographically signed: nobody but the original signer can ever publish a set that a wallet will accept as legitimate, open-source code or not. ### Who Receives the Card The card always follows the same address as the coin reward: whoever is actually named in the block's payout is who the card belongs to. There's no separate "card recipient" field anywhere in the protocol — it's the same payout address, read the same way, every time. If you're mining solo through your own stratum bridge, or through a solo-style pool such as hashnomletz.com that pays each block straight to the miner who found it, that's unambiguous: your address is the one in the payout, so the card is yours. Mining through a pool changes that only if the pool's own payout structure changes it. A pool that instead collects block rewards into its own wallet and settles individual miners' shares separately (common for fee-based, shared-payout pools) would, under that same rule, receive the card itself first. Whether and how it then forwards that card to the actual finder is a policy that pool sets on its own — the Undercroft protocol has no way to see through pool-internal accounting to know who really found the block. Treat a pool's card-custody policy as worth checking before you point hardware at it, the same way you'd check its fee. If a block's payout is split across more than one address, there's no single owner to give the card to, so that block reveals no card for anyone. It counts as a clean block, and the coin reward is unaffected. ## World & Setting The cards exist inside an original setting — a world where AI has taken the surface, and the people who remain survive underground, mining what's left. The full story is intentionally being told gradually, set by set, rather than dumped all at once at launch. That's a deliberate choice, not something left unfinished: the coin's value was never meant to depend on keeping up with a constant stream of lore just to stay engaged. ## Supply & Launch Terms There is no premine. Every UCFT in existence, from block one onward, is mined the same way, by whoever mines it. No portion of any block reward is set aside for the project, its creator, or anyone else — the entire reward goes to the miner who found the block. ## How to Get Involved The Undercroft ships with a full desktop wallet (Windows, with the daemon bundled in) that runs your own full node and holds your coins and cards. Miners can point their ASICs at the hashnomletz.com pool from launch, or solo mine through their own stratum bridge. Linux support is available by running from source at launch, with a packaged build planned as a follow-up once the network is established. ## Technical Specifications - Base: Bitcoin Core v25.0, SHA256d proof-of-work - Target block time: 90 seconds - Difficulty retarget: Dark Gravity Wave, adjusted every block - Initial block reward: 50 UCFT - Halving interval: every 350,000 blocks (~1 year at target spacing) - Maximum supply: ~35,000,000 UCFT - Premine: none - Developer fee: none - P2P port: 23857 · RPC port: 23856 ## A Note on Trust The wallet and daemon source code are open. Nothing about how mining rewards, difficulty, or card odds work has to be taken on faith — it can be read directly. The one thing that stays under the original creator's control is signing off on new card sets, enforced with real cryptography (Ed25519 signatures), not just a promise — so the code can be fully open without opening the door to anyone else publishing a fake set. ## Closing The Undercroft is a real, independently running coin, built and tested by one person as a genuine passion project — not a fundraising pitch, and not a promise about where its price will go. It's an attempt to build something technically sound and actually fun to participate in, mineable by anyone willing to point a SHA256 miner at it.