Re: [Bitcoin-development] [ann] Bitcoin Core 0.9.3 has been released

[Peter Todd <pete@petertodd.org>]

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On Sat, Sep 27, 2014 at 09:32:02PM +0200, Melvin Carvalho wrote:
> > As well as everyone that helped translating on
> > [Transifex](https://www.transifex.com/projects/p/bitcoin/).
> >
> 
> Great work!
> 
> Apologies if this has been covered.  But I was curious about:
> 
> - Increase IsStandard() scriptSig length
> 
> Is there some place I read more to understand this change?

commit 84fe0ffd685627689bbbcd14cf419938f2a100b2
Author: Peter Todd <pete@petertodd.org>
Date:   Mon Mar 10 16:38:44 2014 -0400

    Increase IsStandard() scriptSig length

    Removes the limits on number of pubkeys for P2SH CHECKMULTISIG outputs.
    Previously with the 500 byte scriptSig limit there were odd restrictions
    where even a 1-of-12 P2SH could be spent in a standard transaction(1),
    yet multisig scriptPubKey's requiring more signatures quickly ran out of
    scriptSig space.

    From a "stuff-data-in-the-blockchain" point of view not much has changed
    as with the prior commit now only allowing the dummy value to be null
    the newly allowed scriptSig space can only be used for signatures. In
    any case, just using more outputs is trivial and doesn't cost much.

    1) See 779b519480d8c5346de6e635119c7ee772e97ec872240c45e558f582a37b4b73
       Mined by BTC Guild.

diff --git a/src/main.cpp b/src/main.cpp
index a0b6842..63b87b8 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -513,10 +513,14 @@ bool IsStandardTx(const CTransaction& tx, string& reason)

     BOOST_FOREACH(const CTxIn& txin, tx.vin)
     {
-        // Biggest 'standard' txin is a 3-signature 3-of-3 CHECKMULTISIG
-        // pay-to-script-hash, which is 3 ~80-byte signatures, 3
-        // ~65-byte public keys, plus a few script ops.
-        if (txin.scriptSig.size() > 500) {
+        // Biggest 'standard' txin is a 15-of-15 P2SH multisig with compressed
+        // keys. (remember the 520 byte limit on redeemScript size) That works
+        // out to a (15*(33+1))+3=513 byte redeemScript, 513+1+15*(73+1)=1624
+        // bytes of scriptSig, which we round off to 1650 bytes for some minor
+        // future-proofing. That's also enough to spend a 20-of-20
+        // CHECKMULTISIG scriptPubKey, though such a scriptPubKey is not
+        // considered standard)
+        if (txin.scriptSig.size() > 1650) {
             reason = "scriptsig-size";
             return false;
         }

-- 
'peter'[:-1]@petertodd.org
0000000000000000188beaebec22c62bcff1a5d92e5d21432e797ec717cfed3a

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