Bitcoin: document native C and Windows security alignment

Author: mearvk

bitcoin/REVISIONS-2026-09-16-native.md

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+# Bitcoin Native/Platform Revisions — 2026-09-16
+
+## C implementation
+
+`linux/c/bitcoin/base/BitcoinBase.c` was brought into alignment with the hardened Java Bitcoin boundary.
+
+- Removed RPC password and empty password flags.
+- Uses `BITCOIN_RPC_PORT` with a validated default of `2222`.
+- Uses Bitcoin Core cookie authentication through `bitcoin-cli` rather than command-line credentials.
+- Replaced shell-based `popen()`/`system()` command execution with `fork()`/`execvp()` argument-based execution.
+- Added bounded process waiting and forced termination on timeout.
+- Keeps stderr/stdout inside the controlled child-process pipe.
+- Disabled destructive wallet deletion instead of issuing `rm -r`.
+- Keeps wallet creation/load/unload as explicit Bitcoin Core operations.
+- Keeps transaction broadcasting disabled in the placeholder `send_local_to_remote` path.
+
+## Windows installer
+
+`scripts/windows/bitcoin/windows.install.bat` was updated to:
+
+- stop generating placeholder `rpcuser` and `rpcpassword` credentials;
+- configure local regtest mode;
+- bind RPC to `127.0.0.1`;
+- use a defined local RPC port;
+- perform the Bitcoin Core health check through the same regtest endpoint;
+- return a non-zero exit status when the health check fails.
+
+## Remaining platform verification
+
+The native C implementation and Windows script have been source-updated, but a native compiler run and Windows execution are not claimed from source inspection alone. Those environments should be exercised in CI or on their target systems.