The seed was the hash of the first block seen after the close, so a miner holding tickets
could withhold blocks until one made them win, the active Electrum server could pick which
real block was used by not announcing another (a failed corroboration even moved the draw to
the next block), and the participant order was the server-only `broadcast_at` with no
tie-break, so nobody could recompute the result.
- Open: every round gets a 32-byte `server_seed`, stored only Fernet-encrypted with the
master-xprv key (`server_seed_enc`), with its published `server_seed_hash`;
`draw_confirmations` is copied from round_config. The plaintext column is written only by
the reveal.
- Entering `drawing` (one transaction, `draw_committed` audit row): participants ordered by
bet txid, each `draw_position`, `participants_hash` (sha256 of `txid:vout:address\n`
lines; new `bet_vout`), `draw_height = tip_at_close + 1`. A tip of 0 keeps the round
`closing` (`draw_baseline_tip_unknown`, once per round). All persisted, so a resumed draw
reads rather than recomputes (the `_tick` branch itself is B-81).
- `_complete_draw` / `_wait_for_draw_block` replace `_wait_for_next_block`: wait for
`draw_confirmations` blocks from `draw_height`, then `ElectrumListener.agreed_block_hash`
asks every server, the active one included, for the header at that exact height (valid
work, >= 2 other answers, strict majority of all); no agreement means the same height is
asked again and `draw_header_corroboration_failed` is written once per distinct reported
hash. `draw_stalled` now counts from the last tip advance, or from when the quorum started
to fail. Seed = sha256(server_seed || block_hash || participants_hash), index = seed mod n.
- The winner, the seed and the reveal (`server_seed`, `winner_drawn` payload) are written in
one transaction; a round closing with no participants reveals too. A round opened before
this change (no commitment) is given a secret as it enters `drawing`.
- `GET /rounds/{id}/proof` (public, 404 `round_not_found`, translated in all 7 languages) and
the new fields on `GET /rounds/current`; `draw_confirmations` in `/admin/config` and the
/admin form; `server_seed_hash`/`draw_height` in `/admin/rounds`, never the secret.
- Alembic d3e8b15a7c42 (plain add_column / create_index, expression indexes untouched).
- Docs: the B-73 `*Stato:*`/`*Oggi:*` lines are gone, guides and CLAUDE.md describe the new
draw. Ambiguities resolved in api.md: the proof's participants also carry `amount_sats`
(RND-37 lists it); `seed` is decimal in the proof and hex in the audit row, as specified.
Tests changed because the spec changed: ElectrumListener.corroborate_header (asked only the
other servers about the block the active one announced) is replaced by agreed_block_hash and
its quorum tests ported; draw_winner takes the secret and the list fingerprint; the four
_wait_for_next_block scheduler tests are replaced by _wait_for_draw_block ones (fixed height,
confirmations, same-height retry, stall clock). New: test_draw_proof.py recomputes the winner
independently from the public proof, checks the plaintext secret is nowhere in the database,
the API or the log before the reveal, and that a second pass over a `drawing` round yields
the same winner. Mutation-checked: ordering by broadcast_at, an early reveal and asking the
tip instead of the draw height each fail tests.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
A header only had to meet the target it declared for itself, so a fabricated one with
`bits = 0x207fffff` passed half the time, a jump of several blocks was accepted without
being linked to the tip (a fake header at a huge height locked `tip_height` and froze every
draw), and an ordinary one-block reorganisation closed the session on every server.
- draw.py: MAINNET_POW_LIMIT (00000000ffff...ffff); header_meets_its_own_target also
refuses a claimed target easier than POW_LIMIT.
- ElectrumListener._apply_header is async and takes the active client. A single block must
chain by prev_hash; a jump downloads the headers in between (blockchain.block.headers,
at most 2016 per request, ElectrumClient.get_block_headers) and each must carry valid
work and chain, otherwise HeaderValidationError ends the session.
- The listener keeps the last 10 headers (`_window`), built from the process's first header
and its 9 predecessors (which must chain into it). A header that does not join the tip is
walked back to its fork point inside the window and the server's branch is followed
instead of ending the session; a fork older than the window, or a branch that does not
end at the announced header, still ends it. The audit row and the pause for deep reorgs
are B-85; a competing header at the tip's own height is still ignored until then.
- _header_at also serves older heights from the window.
Tests changed because the spec changed: the mainnet powLimit cannot be mined in a test, so
tests/unit/conftest.py swaps in a regtest limit at import time (the new tests put the real
one back); the _apply_header tests are async; the two _run_once tests serve the first
header's 9 predecessors; test_apply_header_skips_linkage_check_across_a_height_gap is
replaced by the jump tests, since that behaviour is exactly what the finding removed.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
The two Mermaid diagrams under flowchart/ described the intended flow but
had drifted from the code and carried no link back to it. docs/ now holds
the specification instead: 15 Italian documents (flows, architecture, data
model, API, security, audit log, operations, decisions and limits, bug
history) with 472 numbered requirements, each pointing at the function
that implements it and the test that covers it. docs/processo-di-modifica.md
defines the ID convention and the spec -> code -> test change workflow, and
CLAUDE.md now names docs/ as authoritative.
Writing the spec from the code also corrected stale claims in CLAUDE.md
(B-41's get_history check, BUGS.md still tracking B-71/B-72, Cache-Control
scope, the error contract's bare-string exceptions) and in the operator
guides (payouts do retry, only `drawing` fails to resume, rounds do not
open without fee_address). The B-70 doc test now pins the prose in
docs/scommesse-e-prelievi.md instead of the deleted diagram.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
A single hostile Electrum server, or a MITM on the one active
connection, could fabricate the block header the draw's entropy comes
from and so pick the winner of every round: headers were accepted with
no proof-of-work check and no link to the previous tip.
app/rounds/draw.py adds header_meets_its_own_target (rejects a header
whose hash doesn't satisfy the difficulty target it claims) and
header_prev_hash. electrum/listener.py's _apply_header now rejects a
header failing either check by raising HeaderValidationError, which
ends the session the same way a dropped connection would so the
listener rotates to the next configured server.
ElectrumListener gains corroborate_header: before the draw uses a
block, it's independently checked against the other configured servers
and needs a majority to agree. rounds/scheduler.py's
_wait_for_next_block now calls this and, on failure, logs why and
waits for a further block instead of ever using an uncorroborated
header.
Certificate/hostname verification stays disabled, so this doesn't
cover an attacker able to MITM every configured server at once -
BUGS.md notes that as not covered.
Suite grows from 151 to 165 tests. BUGS.md moves B-28 to Previously
fixed.
Periodic scheduler (configurable round duration) that closes a round
only once all broadcast bets confirm, waits for the next block after
closing, draws a winner via block-hash-seeded modulo over participants
ordered by broadcast time, triggers the 70/30 payout, and only opens the
next round once that payout confirms. Draw logic is isolated in
draw.py as a deliberately simple, replaceable component.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
davideandClaude Sonnet 5.5