Website: https://sha256coin.eu/ Block Explorer: https://explorer.sha256coin.eu/
S256 is a Bitcoin fork that takes the contrarian approach: "Double the Work, Double the Value"
Based on Bitcoin Core v31.1, S256 doubles key parameters for increased scarcity and deliberation:
Mandatory upgrade before mainnet block 17,500, where merged mining starts.
- Merged-mining consensus fixes — the auxpow must now prove the merge-mining tag is in the parent block's coinbase, and the hash in the tag uses the same byte order as Namecoin and Dogecoin. Nodes older than 3.0.0 will split off at the first merge-mined block. Merge-mining proxies must be updated: see POOL_PROXY_NOTE.md.
- Crash fixes — nodes holding merge-mined blocks could crash serving their headers to syncing peers, and could fail to restart.
- Protocol version 70100 —
headersmessages are limited by size as well as count, for large merge-mined headers. - Pool nodes — a node restarted after a long gap between blocks serves templates straight away (default
-maxtipageis now 7 days), andcreateauxblockreuses its template and reserves room for the auxpow. MAX_MONEYraised to 84 million, matching S256's total supply.- Testnet3 reset; no default signet (
-signetnow requires-signetchallenge).
Full details: doc/release-notes.md.
Rebased onto upstream Bitcoin Core v31.1 (from v30.0), carrying forward roughly a year and a half of upstream fixes and improvements, plus:
- Testnet fixes — testnet3 and testnet4 nodes were silently connecting to the real Bitcoin test networks instead of S256's own (unmodified network magic bytes and DNS/fixed seeds inherited from upstream); both are now properly isolated on their own network identity, with freshly mined genesis blocks and working difficulty adjustment.
- Fixed a persistent sync warning — "unknown new rules activated (versionbit 2)" no longer appears in bitcoin-qt or the daemon after every sync.
- Critical fix caught before it could ship — this rebase briefly introduced a bug that would have crashed every node on its very first sync (a missing anti-DoS parameter for header synchronization); found via a live sync test against real mainnet peers, fixed, and re-verified before release. It was never active on any released version.
- Pre-fork validation — rehearsed the upcoming AuxPoW/LWMA transition at block 17,500 end to end, including a simulated hashrate drop and recovery, to check LWMA's difficulty response before the real fork happens. See Pre-Fork Validation below.
- Automated releases — tagged releases now build and publish Linux and Windows binaries automatically.
- Substantially hardened unit test coverage across key encoding, descriptors, and the P2P transport layer.
A coordinated hard fork activating at block 17,500 on mainnet, bundling two consensus changes plus network/RPC improvements:
- AuxPoW (merged mining) — other SHA256 coins' pools can now merge-mine S256 alongside their own chain at no extra cost to their miners' hashrate. S256 itself is unaffected either way: legacy (non-AuxPoW) blocks remain valid forever, before and after activation. See AuxPoW / Merged Mining below.
- LWMA difficulty adjustment — replaces the classic 1,008-block-window DAA with per-block LWMA (96-block window) from block 17,500 onward. The old DAA could leave the chain stuck at a too-high difficulty for up to a full 1,008-block window if hashrate dropped suddenly; LWMA responds within a handful of blocks instead.
- Additional DNS + fixed seed nodes for more resilient peer discovery (previously a single point of failure).
- RPC help text fixes — example amounts now correctly show
S256instead of a leftoverBTC. - v2.0.1: fixes two AuxPoW bugs found by new end-to-end test coverage before activation — a merge-mining tag nonce that was incorrectly tied to the parent header's own mining nonce (would have made merge-mining computationally infeasible), and a hash-timing mismatch between
createauxblockand validation that would have made everysubmitauxblockcall fail. Neither was ever active on mainnet (both predate block 17,500), so no chain impact — see the v2.0.1 commit for details.
| Parameter | Bitcoin | S256 |
|---|---|---|
| Block Time | 10 minutes | 20 minutes |
| Block Reward | 50 BTC | 100 S256 |
| Total Supply | 21 million | 84 million |
| Halving Interval | 210,000 blocks (~4 years) | 420,000 blocks (~16 years) |
| Coinbase Maturity | 100 confirmations | 200 confirmations |
| Algorithm | SHA256 (PoW) | SHA256 (PoW) |
- Port: 25256
- RPC Port: 25332
- Address Prefix: S (e.g., S1A2B3C...)
- Script Address Prefix: 8
- Bech32 HRP: s2
- Magic Bytes: 0xf1, 0xc2, 0xa5, 0xd8
- DNS Seeds:
seednode.sha256coin.eu,s256seednode.bitcoinsilver.eu,sha256-mining.go.ro - Fixed Seeds: hardcoded fallback peer IPs baked into the binary (see
contrib/seeds/nodes_main.txt), so peer discovery still works if DNS is unavailable
- Hash:
00000000abe2a78ceb00eca81258804d59fe4ad45345e1750e705139e6da7297 - Timestamp: November 30, 2025
- Message: "S256 2025-11-30 Double the Work Double the Value"
Download Current Compiled Binaries from the Official Web Site: https://sha256coin.eu/#downloads
Refer to the build documentation in the doc/ folder:
- Linux: doc/build-unix.md
- Windows: doc/build-windows.md
- macOS: doc/build-osx.md
# Install dependencies (Ubuntu/Debian)
sudo apt-get update
sudo apt-get install build-essential cmake pkg-config \
libssl-dev libevent-dev libboost-all-dev libsqlite3-dev
# Build
cmake -B build
cmake --build build -j$(nproc)
# Binaries will be in: build/bin/# Install all dependencies including Qt libraries (Ubuntu/Debian)
sudo apt-get update
sudo apt-get install build-essential cmake pkg-config \
libssl-dev libevent-dev libboost-all-dev libsqlite3-dev \
libxcb-icccm4 libxcb-image0 libxcb-keysyms1 libxcb-render-util0 \
libxcb-xinerama0 libxcb-xkb1 libxkbcommon-x11-0 libfontconfig1 \
libfreetype6
# Build with GUI enabled
cmake -B build -DBUILD_GUI=ON
cmake --build build -j$(nproc)
# GUI wallet: build/bin/sha256coin-qt
# Daemon: build/bin/sha256coind
# CLI: build/bin/sha256coin-cliNote: If you get "library not found" errors when running the GUI, install the missing Qt/X11 libraries listed above.
# Install mingw-w64
sudo apt-get install g++-mingw-w64-x86-64
# Configure and build
cmake -B build-win \
-DCMAKE_TOOLCHAIN_FILE=cmake/toolchains/x86_64-w64-mingw32.cmake \
-DBUILD_GUI=OFF
cmake --build build-win -j$(nproc)
# Windows binaries will be in: build-win/bin/./build/bin/bitcoind -daemon./build/bin/bitcoin-cli getblockchaininfo./build/bin/bitcoin-cli stopLinux: ~/.sha256coin/
Windows: %APPDATA%\SHA256Coin\
macOS: ~/Library/Application Support/SHA256Coin/
Create sha256coin.conf in your data directory for custom settings:
# RPC Settings
rpcuser=yourusername
rpcpassword=yourpassword
rpcallowip=127.0.0.1
# Network
port=25256
rpcport=25332
# Optional: Add nodes
addnode=sha256coin.eu:25256S256 uses SHA256 Proof-of-Work, compatible with Bitcoin mining hardware (ASICs).
Solo Mining:
./bitcoin-cli generatetoaddress 1 "your_s256_address"Pool Mining: Contact pool operators or set up your own using sha256-nomp.
Starting at block 17,500, S256 supports auxiliary proof-of-work (AuxPoW), the same merged-mining mechanism used by Namecoin, Dogecoin, and other coins. Any other SHA256 chain's pool can merge-mine S256 alongside its own block, at no extra cost to its miners' hashrate.
- Chain ID:
598(0x0256) - RPC methods:
createauxblock <address>returns a new S256 block template to embed in the parent chain's coinbase;submitauxblock <hash> <auxpow-hex>submits the completed proof once the parent pool has mined a qualifying block. - Compatibility: legacy (non-AuxPoW) blocks remain valid at every height, before and after activation — solo miners and existing pools are unaffected.
Pool and proxy operators: v3.0.0 changes the byte order of the hash in the merge-mining tag and requires the coinbase merkle index to be 0. See POOL_PROXY_NOTE.md for the exact tag layout, examples, timing and how to check.
Pools that tested merged mining with v3.0.1 on testnet3:
See src/auxpow.h/src/auxpow.cpp for the AuxPoW proof format and validation, and src/rpc/mining.cpp
for the RPC implementation.
Before block 17,500 activates on mainnet, the AuxPoW/LWMA transition was rehearsed end-to-end on an isolated test chain — including a simulated hashrate drop and recovery, to check how LWMA's per-block difficulty adjustment responds when miners come and go. See the full report with charts:
https://sha256coin.github.io/s256-core/test/lwma-transition-test.html
(source: public/test/lwma-transition-test.html)
- Website: https://sha256coin.eu/
- Block Explorer: https://explorer.sha256coin.eu/
- GitHub: https://github.com/sha256coin
- Discord: https://discord.gg/dtn58HrC94
- Telegram: https://t.me/+Ecf4ApES37NjZTBk
"Digital Platinum" - Because excellence takes effort.
S256 embraces difficulty rather than avoiding it:
- Harder to mine, not easier
- Longer block times for deliberation
- True scarcity through proof of real work
- Exchange Deposits: 500+ confirmations recommended
- Consensus: Pure Proof-of-Work
- Difficulty Adjustment: Classic 1,008-block window (~14 days) below block 17,500; per-block LWMA (96-block window) from block 17,500 onward — see What's New in v2.0.1
S256 Core is released under the terms of the MIT license. See COPYING for more information or see https://opensource.org/license/MIT.
S256 is based on Bitcoin Core v31.1 and maintains compatibility with Bitcoin's proven codebase while implementing the 2x parameter modifications.
For technical details on the modifications, see the documentation in the /doc folder.
Fork of Bitcoin Core - Modified for S256 specifications