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Data processing findings — Bitcoin complex-network study

Status: dataset acquired, extraction code ported and applied end-to-end to real chain data. Date: 2026-10-02

1. The paper's dataset (downloaded, verified)

Source: https://dynamics.cs.washington.edu/nobackup/bitcoin/bitcoin.tar.gz

  • 678,858,686 bytes; last modified 2018-01-19; sha256 3dfda89e481ec26051a9cca819698486ae5e38236dbe7f3d21da00491eabf499
  • Landing page https://dynamics.cs.washington.edu/data.html is now an archival, unmaintained UW collection.

Contents: GraphLab SFrame (bitcoin.vertices.sframe/, bitcoin.links.sframe/) plus CSV exports:

  • bitcoin.vertices.csv — vid, first_transaction_date — 6,336,769 users
  • bitcoin.links.csv — dst_id, src_id, count, maxdate, mindate — 16,057,711 directed user pairs, sum(count) = 28,143,065 transactions, 5,397,167 sources / 6,229,737 destinations, 2009-01-11 → 2013-04-10, zero self-loops (src == dst count = 0)

Critical: this is an already-clustered, pair-aggregated graph. It is NOT an input to the extraction code, and the per-transaction edge list behind the paper's Table 1 is not in it. The published graph also has self-loops removed, which matters (see §4).

2. Extraction code (ported)

Original: github.com/ivanbrugere/Bitcoin-Transaction-Network-Extraction (branch master), Python 2 (bsddb, print statements, has_key), written 2012-2013, reads a raw text dump produced by Harrigan's bitcointools fork (dbdump.py --all-transactions).

Faithful Python 3 port in code/btc_py3/ (algorithm unchanged; only bsddb → in-memory HashDB shim, print syntax, list semantics): process_bitcoin_network.py, write_network_dictionaries.py, fix_missing_public_keys.py, write_user_public_keys.py, write_user_edges.py, hashdb.py

Input format:

in  <own_txid> <referent_txid> <input_index> <pubkey> <date>
out <own_txid> <output_index> <pubkey> <value_btc> <date>

Outputs: transactionkey_list.txt, pubkey_list.txt, userkey_list.txt, user_edge_inputs.txt, user_edge_input_public_keys.txt, and the main file user_edges.txt = [tx_id, user_from, user_to, date, value_btc].

Validated with a synthetic input exercising every path (coinbase → self-loop, change-address self-loop, multi-input cluster merge, (None) bucket). Result matched predictions exactly.

3. Bridge from the AWS Open Data parquet

scripts/download_parquet_days.py → scripts/gen_transactions_txt.py (public bucket s3://aws-public-blockchain/v1.0/btc/, HTTP, no credentials).

Two format traps found by inspection — both silent, neither self-announcing:

  1. Timestamp must be a single whitespace-free token of ≥19 chars. The parser slices fixed character positions 0:4,5:7,8:10,11:13,14:16,17:19, so an ISO T separator works and a space silently drops HH:MM:SS (and does NOT error).
  2. Coinbase txs must emit only their out lines (the original dump tagged their referent coinbase and the parser skips those). That is the mechanism by which coinbase rewards become self-loop edges downstream.

Node identity in early data (the big one)

The ETL leaves address NULL for pay-to-pubkey scripts — i.e. essentially all early mining rewards. In the 2010 window measured: 29.15% of outputs and 24.65% of inputs had no address. Bucketing them as (None) would collapse a quarter of early nodes into one pseudo-hub and destroy the graph. Recovery:

  • Outputs: the pubkey is inline in script_hex — 41|21 <pubkey> ac (134 / 70 hex chars, note 65-byte uncompressed pubkeys, not 64). → 29.15% → 0.001% unresolved.
  • Inputs: the ETL stores only the signature in a P2PK spend's script_hex (no pubkey, no address). Recovered by back-joining to the consumed output on (spent_transaction_hash, spent_output_index). → 24.65% → 0.000% unresolved.

Schema drift across partitions — CORRECTED, it is NOT data loss

The AWS transactions table shows three variants, interleaved day by day:

  • 255 days: no inputs column at all
  • 18 days: inputs present but outputs has no address
  • 450 days: complete

Earlier I recorded that "those 255 days cannot yield edges or clustering". That was wrong. Two exhaustive tests over all 723 local 2009-2010 partitions show the drift is empty-column omission by the ETL writer, i.e. information-preserving:

Test A — inputs column present <=> the day has at least one non-coinbase transaction

inputs absent  & 0 non-coinbase txs : 255 days
inputs present & >=1 non-coinbase   : 468 days

Zero exceptions. And because coinbase transactions carry no inputs by construction (they are NULL even in complete partitions), a day with no non-coinbase transaction loses nothing:

  • 2009 degraded days: 20,628 txs, 20,628 coinbase, 0 non-coinbase
  • 2010 degraded days: 1,893 txs, 1,893 coinbase, 0 non-coinbase
  • non-coinbase transactions lost across 2009-2010: 0 of 117,604 (0.00%)

Test C — outputs.address absent <=> every output on that day is P2PK

273/273 no-address days have 100% type='pubkey' outputs
0 days with any non-P2PK output lack the field

Control: on complete days P2PK outputs still carry address = NULL, but the column exists because at least one output is pubkeyhash. So the writer drops a column only when it is entirely empty for that partition.

Consequences

  • No repair from Blockchair/BigQuery is needed; the plan to reconstruct 255 days is cancelled.
  • All 723 days of 2009-2010 are usable. 2009 is 358/358 usable: 243 of its days are coinbase-only (mining rewards), whose edges come from the output side, which every variant has.
  • The only lost capability on those days is input-side verification of spends — and the spend count there is zero.
  • read_parquet(union_by_name=true) is still required to read the corpus (different struct types across files), and DuckDB 1.5.6 hits an internal error on UNNEST + aggregate over a union of differing struct types — scan partitions per-file when that bites.

4. Result of applying the extraction to real data

Window 2010-01-21 → 2010-12-31 (345 complete-schema days), 3.0 s runtime:

quantity value
transactions in window (parquet) 182,229
transactions recovered by extraction 182,227 (99.999%)
coinbase transactions 64,857
addresses/pubkeys indexed 145,606
users (clusters) 98,063
edges (user_edges.txt) 230,603
self-loops 104,231 = 45.2%
largest user cluster 928 pubkeys
max user degree 11,042

Consistency check: 528.2 tx/day in the window vs blockchain.com's 2010 daily mean of 508/day.

Reconciliation flag: the extraction emits 45.2% self-loops, while the published links.csv has zero. The published graph was therefore filtered or built by a different aggregation, and the paper's node/link counts do not reproduce from the tarball alone (1P: tarball gives 111,017 pairs vs the paper's 302,116 links; 2P: 11,147,849 pairs vs 11,432,100). Reproducing the paper requires running this pipeline, not using the tarball.

6. Network size: my numbers vs the paper

What the paper states

  • Methods: "more than 25 million links (transactions) and more than 5 million nodes (users)", data 01 Jan 2009 → 08 Jan 2013.
  • Table 2: 1P (2009-2010): 193,012 nodes, 302,116 links, avg degree 1.565, clustering 0.116. 2P (2011-2012): 4,689,069 nodes, 11,432,100 links, avg degree 2.438, clustering 0.24.

Measured values

quantity paper published tarball raw chain (my measurement)
total transactions ">25 M" 28,143,065 2009-2010 only: 218,014
total users ">5 M" 6,336,769 vertices —
1P nodes 193,012 110,057 (−43%) 176,343 distinct output addresses (−9%)
1P links 302,116 111,017 pairs (−63%) 266,467 outputs = one edge each (−12%)
2P nodes 4,689,069 4,601,334 first-seen 2011-12 (−1.9%) not downloaded
2P links 11,432,100 11,148,049 pairs (−2.5%) not downloaded
1P+2P nodes 4,882,081 4,711,391 (−3.5%) —

My own extraction run (2010-01-21 → 2010-12-31, 345 days) produced 98,063 users / 230,603 edges from 182,227 transactions, against a raw-chain count of 182,229 transactions and 230,603 outputs in the same window — i.e. the port reproduces the chain exactly under its own definition (one edge per output, users = multi-input clusters, self-loops included).

Where the two agree, and where they do not

  • Agrees: total scale (28.1M vs ">25M" transactions; 6.34M vs ">5M" users), the 2P period (−2%), and the 1P+2P node total (−3.5%).
  • Disagrees: the 1P split. The paper's 1P is 75% larger in nodes and 172% larger in links than the dataset it cites.

Mechanism (measured, not guessed)

The published tarball excludes coinbase transactions and all self-loops:

  • links.csv has exactly 0 self-loops (src == dst).
  • 2009 on chain: 32,709 transactions, of which 32,490 are coinbase → only 219 non-coinbase. The tarball lists 218 transactions for 2009. That is a direct proof of the filter.
  • 1P coinbase transactions are 100,410 of 218,014 = 46%. Coinbase outputs are the mining-reward self-loops that the extraction code does emit (verified in the unit test and in my run).

So the paper's 1P figures are consistent with address-level counting that includes mining activity (176k addresses / 266k outputs, within 9-12%), while the published graph is user-clustered, coinbase-free, self-loop-free, pair-aggregated (110k / 111k). The residual ~12% on 1P links is not explained by this alone and remains open.

Consequence for the study

The tarball cannot be used as a drop-in baseline: it under-covers the first period by ~40% of chain transactions (130,739 vs 218,014) once coinbase is removed, and it silently drops 45% of edges as self-loops in the window I measured. Any comparison against the paper must state the inclusion policy for (a) coinbase, (b) self-loops, (c) edge aggregation (per-output vs per-pair), and (d) node entity level (address vs user) — all four change the numbers by 2-3x.

8. Which files can build temporal networks (verified)

A temporal network needs edge endpoints + a per-event time. Only some of what we hold qualifies.

Tier 1 - true link streams (per-event timestamps)

runs/2010_window/user_edges.txt - the extraction output, the direct analogue of the paper's Table 1. Rows are [tx_id, user_from, user_to, date, value_btc].

  • 230,603 edges, 98,063 users, 14-digit second-resolution timestamps, 20100121000527 -> 20101231235450, 345 days, 64,806 distinct timestamps, 115-11,783 edges/day (100x swing).
  • Includes the 45.2% self-loops; policy must be declared.

data/parquet/ - address-level raw material, edge = (input address -> output address) with block_timestamp, block_number, index (position in block), value.

  • Local: 2009-01-03 -> 2010-12-31, 723 days, but 255 days have no inputs column, so no in-edges for those days. 64,857 blocks / 64,806 distinct second-timestamps in the clean window; index reaches 849, so intra-block order is recoverable via (block_number, index).
  • Whole history 2009 -> 2026 is available from the same bucket (2.19 TB) with the same schema.

Tier 2 - interval/aggregated temporal only (NOT link streams)

data/bitcoin/bitcoin.links.csv - dst_id, src_id, count, maxdate, mindate. 16,057,711 pairs spanning 1,294 distinct mindate days (2009-01-11 -> 2013-04-10). Each row carries only the FIRST and LAST date plus a count, so the count individual interactions cannot be placed in time. Supports: edge-interval/active-period analysis, coarse first-seen timelines. Does NOT support: inter-event times, burstiness, snapshot sequences with correct edge sets, and critically not the paper's own attachment analysis - testing degree/wealth/fitness preferential attachment requires, for each new node, the degree of its target at that instant, which the aggregation has destroyed.

data/bitcoin/bitcoin.vertices.csv - vid, first_transaction_date: node birth times for 6,336,769 users (2009-01-03 -> 2013-04-10). Node-appearance process only, no edges.

Tier 3 - external temporal covariates (not networks)

Daily/weekly series (tx/day, price) for activity-vs-price correlations; daily counts already pulled for 2009-2026.

Temporal caveats

  • The honest causal granularity is the block, not the second: block timestamps are miner-set (bounded only by median-time-past), and within a block ordering is the miner's, recoverable via index. Sub-second/burst analysis below block level is not defensible.
  • Self-loops (45.2%) and coinbase edges are structural artifacts; decide before building.
  • For 2011+ windows, only the parquet path scales; the tarball stops at 2013-04-10.

10. Full paper-window run (in progress)

Downloaded the paper's exact window: 1,462 partitions, 15.06 GB, 0 unreadable (2009-01-03 -> 2013-01-08). Schema scan over the new period:

inputs=True  addr=True  : 1189 days
inputs=False addr=False :  255 days   (all in 2009-2010)
inputs=True  addr=False :   18 days   (all in 2009-2010)
per year: 2009 243/358 without inputs, 2010 12/365, 2011 0/365, 2012 0/366, 2013 0/8
ETL write batches: 2026-02-06 (1222 partitions), 2026-02-07 (240)

So 2011+ is completely clean, and every degraded day is a 2009-2010 coinbase-only day (consistent with the empty-column-omission mechanism in §3).

Generation to the extraction's input format: 7.9 GB text, 2 min 54 s, peak RSS 25 GB.

Engineering lesson: never ORDER BY inside the COPY

The first two attempts died at the same place. The generator's ORDER BY f1, sortkey forced DuckDB to globally sort ~45M rows: with a 40 GB limit the process was killed externally (no Python traceback); with a 16 GB limit DuckDB raised a clean OutOfMemoryException at 14.9 GiB. Dropping the ORDER BY removes the sort entirely — the extraction code sorts rows itself in fix_missing_public_keys (by 1,2,0) and write_user_edges (by 1,0,2), so the sort was pure waste. Generation then streams. Debugging note: Python's stdout is block-buffered when redirected, so a log that appears to stop early may just be unflushed — re-run with PYTHONUNBUFFERED=1 to see the real point of death.

Extraction status and the 4 GB worker cap

Generation to the extraction's input format: 7.9 GB text, 2 min 54 s, peak RSS 25 GB (22,030,699 in + 25,356,719 out = 47,387,418 rows).

The extraction needs ~6 GB in the dictionary stage and ~13 GB during its first internal sort (measured: 155 bytes/row for the array('L') rows, +120 bytes/row for sort keys). The agent runtime caps background jobs at 4 GB, so every normal attempt died there:

the agent worker scope: memory.max = 4294967296 (4 GB)
                       memory.peak = 4294967296, memory.events max = 67057

_DEFAULT_WORKER_MEMORY_MAX_BYTES = 1 GB, _WORKER_MEMORY_MAX_CAP_BYTES = 4 GB in tools/process_registry.py; every background spawn gets --property MemoryMax=<n>. Foreground calls run in the gateway cgroup (memory.max = max) but are capped at 600 s and the tool refuses setsid/nohup in foreground commands, so heavyweight jobs must go through Docker (own cgroup, unaffected by the scope cap).

Diagnostic traps hit along the way: ps field 10 is CPU time, not wall clock; Python block-buffers stdout when redirected, so a log that "stops early" may just be unflushed (use PYTHONUNBUFFERED=1); and the OOM kill leaves no Python traceback — only journalctl --user shows A process of this unit has been killed by the OOM killer.

Transport hazard (cost one complete 30-minute run): do NOT stream the output tar on the container's stdout. Stray echo lines land in the archive, the host tar aborts with This does not look like a tar archive, the pipe breaks, and --rm then deletes the results. Correct pattern, in scripts/run_full_window_docker.sh: the container writes out.tar into the bind mount, the host extracts it as the normal user (rootless docker has a userns offset, so a container cannot create user-owned files directly).

Single run required: the union-find clustering must see the whole period, or a user active across years would get inconsistent cluster ids (so per-year chunking is not an option). Generation is skipped if the input exists, so the runner is resumable.

11. RESULTS: full paper-window extraction (complete)

Ran in Docker on the paper's exact window (2009-01-03 -> 2013-01-08), 10 minutes wall clock (10:01:41 -> 10:12:10), versus the 4 GB-capped attempts that died every time.

Global output (runs/full_window/out/, 2.6 GB)

quantity value
edges (user_edges.txt) 25,356,719
transactions 10,886,588
distinct users 4,910,855
self-loops 5,878,290 (23.18%)
date span 20090103181505 -> 20130108235206
pubkeys indexed 8,906,547
clusters 4,910,855 (4,400,093 singletons = 89.6%)

Independent validation: the distinct-transaction count (10,886,588) matches blockchain.com's independent daily series for 2011-2012 (10.4M) to within 5%, and the edge count equals exactly the generator's out line count (25,356,719). The port reproduces the chain.

Period split vs the paper's Table 2

period my nodes my edges my self-loops my avg deg paper nodes paper links paper avg deg
1P 2009-2010 71,113 266,467 52.7% 3.747 193,012 302,116 1.565
2P 2011-2012 4,803,046 25,090,252 22.9% 5.224 4,689,069 11,432,100 2.438

Reading:

  • 2P nodes match: 4,803,046 vs 4,689,069 = +2.4%.
  • Global scale matches: 25.36M edges vs ">25M links"; 4.91M users vs ">5M users" (their window runs 3 months further, to 2013-04-10, which explains the shortfall).
  • 1P links are close-ish: 266,467 vs 302,116 = -12%.
  • The paper's two periods use inconsistent link definitions. Their 2P links (11,432,100) match the aggregated distinct-pair count (tarball: 11,148,049, -2.5%), not the per-output edge count (mine: 25,090,252, 2.2x). Their 1P links (302,116) instead match the per-output/address-level count (mine: 266,467, -12%), not the aggregated pairs (tarball: 111,017, -63%). So "links" cannot mean the same thing in both columns, and the paper's 1P figures cannot be reproduced from its own published dataset.
  • 1P nodes off by -63% under the user-clustered definition, but my earlier address-level measurement (176,343 distinct output addresses) sits within 9% of their 193,012 - further evidence that their 1P table reflects address-level counting that includes mining activity.

Structural findings worth carrying into the study

  • Self-loop share collapses over time: 52.7% in 1P -> 22.9% in 2P (coinbase/change self-loops dominate the early network and become a minority as real transfers grow). 97.8% of self-loops are change/other, only ~2.2% carry a ~50 BTC coinbase-like amount.
  • Mega-clusters exist and are large: largest user cluster = 261,808 pubkeys (2.94% of all addresses), then 127,073 / 99,645 / 78,895 / 40,969. The 2010-only window's largest was 928 pubkeys, so the multi-input heuristic collapses massively in the 2011-2013 exchange era (batching/consolidation, plus CoinJoin false merges). Any degree-distribution or preferential-attachment result after ~2011 is dominated by this cluster-structure artifact - it must be measured and either bounded or handled explicitly.
  • 89.6% of users are singletons, so the mean cluster size is 1.81 but the tail is extreme.

12. Next steps (not yet done)

  1. Repair the 255 no-input days + 273 no-address days CANCELLED — not data loss (see §3): both variants are empty-column omission and cost zero edges. The 2009-2010 window is fully usable as-is. Next actual step: run the extraction over 2009-01-03 → 2013-01-08 (the paper's window, now downloaded) and compare with the tarball at pair level.
  2. Decide the self-loop and change-address policy explicitly (45% of edges at user level).
  3. Modern extension (2013 → 2026) once the pipeline is validated on the paper's window.