XID

xCoin (XID) is a proof-of-work cryptocurrency designed to remain secure in a world with large-scale quantum computers. It is a fork of Bitcoin Core, rebuilt so that post-quantum cryptography protects every coin from the first block. Mainnet launched with its genesis block on September 26, 2026. There was no pre-mine, no ICO and no founder or developer allocation. Every XID in circulation has been issued to miners as block rewards. Post-quantum security. xCoin uses the cryptography standards published by NIST in 2024. Coins are secured by ML-DSA-65 signatures (FIPS 204). Each address commits to a small script tree that can also hold a backup spending path secured by SLH-DSA (FIPS 205), a signature scheme based only on hash functions. The consensus rules accept only these post-quantum outputs, so no coin on the chain depends on elliptic-curve keys that a quantum computer could break. Connections between nodes are encrypted, and nodes prefer a hybrid key exchange that combines ML-KEM-768 (FIPS 203) with classical cryptography. Mining. Blocks are mined with MetalDAG, a memory-hard proof-of-work algorithm from the Ethash family. Its dataset was 4 GiB at launch and grows by 128 MiB every two weeks. This favors memory bandwidth over specialized chips and lets consumer graphics hardware, including Apple Silicon Macs, take part. The network targets one block every five minutes and adjusts difficulty with every block. Supply. Total supply is capped at 100,000,000 XID, divisible to eight decimal places. The block reward starts at 6.25 XID and doubles in steps to 50 XID by block 60,001, about seven months after launch. It stays at 50 XID until block 220,000, about two years in, then falls by one tenth roughly every year. Issuance ends around the year 2363, when the cap is reached. Newly mined coins can be spent after 1,000 confirmations, about three and a half days. Network. The peer-to-peer network has been open to community-run nodes since September 27, 2026, with DNS seeds for peer discovery. Miners can choose solo or PPLNS pools in six regions across North America, South America, Europe and Asia. A public block explorer, a pool directory and a faucet that pays small amounts of XID for trying the network are also available. Roadmap. The next priority is liquidity: more trading pairs and exchange listings, so XID can be bought, sold and priced reliably. This lays the groundwork for xPay, a planned payments app for sending, receiving and saving XID, with opt-in savings locks and scheduled payouts. xCoin's node software is open source under the MIT license.