# Bitcoin's script resource limits were retrofitted in mid-2010 **12 August 2026.** Bitcoin Script enforces several resource limits. Four of them cap the size of a pushed stack element, the total script size, the stack depth, and the size of a numeric operand. They are commonly treated as part of the original design. **None of the four is in the January 2009 release.** All four were added on **29 July 2010**, in a single commit whose message describes a makefile change, and the element and numeric caps were tightened seventeen days later by a commit whose message is *"misc changes"*. *(A fifth limit — the op-count cap — arrives separately at v0.3.7 and is noted but not dated here.)* This note dates the four, gives the method to reproduce the dating, and states one consequence. > ### What is already known, and what this note adds > > **The tightening commit is documented in a BIP.** [BIP-347](https://github.com/bitcoin/bips/blob/master/bip-0347.mediawiki) > (OP_CAT reactivation) cites `4bd188c` — *"In 2010, a single commit disabled OP_CAT, along with > another 15 opcodes"* — and records that the element cap stood at 5,000 bytes at that moment: > *"As Bitcoin at that time had a maximum stack element size of 5000 bytes, the effect of this > expansion was limited to 5000 bytes."* > > **BIP-347 does not say when that 5,000-byte cap was introduced.** It establishes that the limit > *existed*; it makes no claim about when it arrived, or about the other three caps. > > ``` > ALREADY DOCUMENTED 4bd188c disabling OP_CAT and 15 opcodes (BIP-347) > that a 5,000-byte element cap existed in 2010 (BIP-347) > > ADDED HERE the DATE OF INTRODUCTION -- 757f076, 29 Jul 2010 > that four caps arrive together in one commit > that the commit message describes only a makefile change > the byte-identity provenance result below > ``` > > **No priority is claimed even for the added part.** A literature search was performed and is > reported here; it was not exhaustive, and the commits are public to anyone who looks. --- ## The finding ``` Jan 2009 v0.1.0 NO LIMITS OF ANY KIND 30 Aug 2009 e071a3f6 "First commit" NO LIMITS 35,279 B 03 Feb 2010 53d5080 NO LIMITS 35,611 B 12 Feb 2010 98500d7 NO LIMITS 35,606 B 14-28 Jul 2010 every commit tested NO LIMITS 34,472 / 35,606 B 29 Jul 2010 17b2740 NO LIMITS 35,606 B <- last uncapped state 29 Jul 2010 757f076 ALL FOUR 39,255 B <- +3,649 bytes 15 Aug 2010 4bd188c TIGHTENED ``` ### The commit that installed them ``` 757f0769d8360ea043f469f3a35f6ec204740446 2010-07-29T20:27:12Z author field: s_nakamoto message: "reverted makefile.unix wx-config -- version 0.3.6" script.cpp +671 -643 (102 of the added lines are blank or brace-only) script.h +26 -1 bignum.h +2 -1 makefile.unix +14 -5 the only file the message refers to serialize.h +2 -2 setup.nsi +3 -3 ``` The additions to `script.cpp` that impose limits: ```diff +static const size_t nMaxNumSize = 258; numeric operand cap + if (script.size() > 20000) script size cap + if (vchPushValue.size() > 5000) pushed element cap + if (stacktop(-1).size() > 5000) + if (stack.size() + altstack.size() > 1000) stack depth cap ``` **Four limits, not five.** The **op-count** limit (`nOpCount > 200`) is **not** in this commit; it arrives at v0.3.7. And the script-size cap here is **20,000**, later tightened to 10,000. So the regime assembles across three releases, with this commit carrying the bulk of it. ### The commit that tightened them ``` 4bd188c4383d6e614e18f79dc337fbabe8464c82 2010-08-15T21:05:16Z author: s_nakamoto SVN r131 shipped in v0.3.10 (08fee752) message: "misc changes" ``` ```diff - if (vchPushValue.size() > 5000) + if (vchPushValue.size() > 520) - if (stacktop(-1).size() > 5000) + if (stacktop(-1).size() > 520) ``` The same commit cuts the numeric cap `258 → 4` and adds a pre-switch guard disabling `OP_CAT`, `OP_SUBSTR`, `OP_MUL` and siblings — the opcode disabling that BIP-347 exists to reverse. > **⚠️ A citation discrepancy, offered as an observation rather than a correction.** BIP-347's > reference for this commit reads *"S. Nakamoto, 'misc changes', **Aug 25 2010**"*. **The commit's > own metadata gives 2010-08-15T21:05:16Z in both the author and committer fields**, and its > `git-svn-id` trailer is `trunk@131`. > > The ten-day gap is not explained by the commit record: the v0.3.10 build commit `08fee752` is also > dated 15 August (22:46:58Z, ninety minutes later), and the commits actually dated 25 August 2010 > are the alert-system and safe-mode changes. **It may correspond to a release or announcement date > rather than the commit; the reference attributes it to the commit.** Nothing in BIP-347's argument > depends on the date, and nothing here contests its substance. > **⇒ Bitcoin Script's resource-limit regime arrived in mid-2010, across three releases, with the > bulk of it in one commit whose message describes a makefile change and the tightening in another > whose message is "misc changes".** **The full assembly, so no step is overstated:** ``` v0.3.6 29 Jul 2010 757f076 element 5000 · script 20000 · stack 1000 · numeric 258 ^ dated here, by fetched file v0.3.7 2010 -- op-count 200 · script 20000 -> 10000 ^ NOT dated here. Stated from secondary reading; the commit was not fetched and this row is not evidence v0.3.10 15 Aug 2010 4bd188c element 5000 -> 520 · numeric 258 -> 4 · opcodes disabled ^ dated here, by fetched commit ``` --- ## Method **No inference. Every row above is a fetched file.** Each commit in `bitcoin/bitcoin` between 30 August 2009 and 15 August 2010 was retrieved at `raw.githubusercontent.com/bitcoin/bitcoin//script.cpp` and tested for the literal cap expressions. The transition is exact and same-day: `17b2740` carries none of them at 35,606 bytes; `757f076` carries all of them at 39,255 bytes. ```bash # reproduce the transition in two fetches for sha in 17b274028 757f0769d; do curl -s "https://raw.githubusercontent.com/bitcoin/bitcoin/$sha/script.cpp" \ | grep -c 'vchPushValue.size() > 5000' done # -> 0 then 1 # and read the installing commit directly gh api repos/bitcoin/bitcoin/commits/757f0769d --jq '.files[] | "\(.filename) +\(.additions) -\(.deletions)"' ``` **Genesis-side confirmation** was executed rather than read. The January 2009 interpreter was compiled from the authentic `script.cpp` and evaluated against the script ` OP_DROP OP_1` at ten sizes from 71 to 17,088 bytes. **It accepts every one.** Its only `.size()` tests are *minimum* stack-depth guards, and push handling is `opcode <= OP_PUSHDATA4` — a four-byte length prefix. --- ## A provenance result, obtained incidentally While fetching `script.cpp` at the first commit of `bitcoin/bitcoin` in order to date the caps, it was compared against the copy preserved in the Satoshi Nakamoto Institute's v0.1.0 archive: ``` bitcoin/bitcoin @ e071a3f6, 30 Aug 2009 35,279 B sha256 347c7526932d42a4d10ae487150b709e… SNI v0.1.0 archive, script.cpp 35,279 B sha256 347c7526932d42a4d10ae487150b709e… BYTE-IDENTICAL ``` **Two things follow.** `script.cpp` was unchanged for seven months, from the January 2009 release to the first commit of the canonical repository. And the archive copy is **independently authenticated against `bitcoin/bitcoin` itself** — for this file, provenance no longer rests on custody and published digests alone. --- ## One consequence, stated as a corollary rather than a motivation The NIST post-quantum signature standards — **ML-DSA (FIPS 204)** and **SLH-DSA (FIPS 205)**, finalised August 2024 — produce signatures far larger than secp256k1's ~71 bytes. Sizes below are the standards' own, measured from OpenSSL 3.5.4 output. Against the dated limits: ``` before 29 Jul 2010 29 Jul – 15 Aug 2010 after 15 Aug 2010 (no limit) (5,000 B element cap) (520 B element cap) ML-DSA-44 2,420 B fits fits no ML-DSA-65 3,309 B fits fits no ML-DSA-87 4,627 B fits fits no SLH-DSA-128s 7,856 B fits no no SLH-DSA-192s 16,224 B fits no no SLH-DSA-128f 17,088 B fits no no ``` **This is an observation about byte sizes against a byte limit, and nothing more.** It does not claim the 2010 commits considered post-quantum cryptography — they plainly did not; both are denial-of-service hardening, seventeen years before the standards existed. It does not claim any post-quantum scheme would have been *usable* in 2009: fitting on the stack is necessary, not sufficient, and says nothing about verification opcodes, transaction size, block capacity or fees. > **What it does establish is narrow and checkable: the constraint that today rules out every > standardised post-quantum signature at the script layer is not a property of Bitcoin's original > design. It was introduced later, for unrelated reasons.** --- ## Limits of this note ``` NOT a novelty claim no literature search was performed; the commits are public NOT a claim about intent the commit messages are quoted, not interpreted. Why script.cpp was rewritten in a commit about makefile.unix is not established here NOT a completeness claim only script.cpp was tracked. Other consensus limits (block size, sigops, transaction size) are not covered NOT a recommendation nothing here argues for or against changing any limit BOUNDED window 30 Aug 2009 to 15 Aug 2010. The repository's history begins at the first commit; the Jan-Aug 2009 interval is covered by the archive copy, which is byte-identical to that first commit ``` --- ## Artifacts The experiment source, its captured output, the fetched upstream `script.cpp`, and the full per-commit dating record are published with a SHA-256 manifest. The reproduction is two `curl` calls; the compiled check requires g++ and the interpreter source. **Corrections to this note will be published, dated, and never made silently.**