# Gavin Andresen
# 2012-01-24 21:51:56
# https://bitcointalk.org/index.php?topic=60950.msg711055#msg711055

@s{quotedtext}
@s{quotedtext}
 @p{brk}
Yes. Old solo mining clients will produce perfectly valid blocks, unless they've been hacked to mine "non-standard" transactions. @p{par}

There is a small risk that somebody ELSE will produce an invalid block, old solo mining clients will think it is valid, and will try to mine on top of it.  But that's a small risk because we'll wait until a super-majority of the network supports p2sh before starting to reject any p2sh transactions. @p{par}

So worst case scenario would be: @p{par}

+ Somebody with a hacked bitcoind mines a block containing a valid-under-old-rules, invalid-under-new p2sh transaction. @p{brk}
+ Old miners try to build on it, but the majority of the network rejects it (there's a short block-chain split). @p{par}

If an attacker could target just the p2sh-supporting nodes and denial-of-service enough of them to get p2sh support below 50%, then there could be a longer block-chain split. If you do the math, that's not as easy as it sounds (if p2sh support is at 80%, you'd have to knock out 60% of the supporting nodes@p{--} 20% of the original network would support, 20% wouldn't...). @p{par}


@s{quotedtext}
@s{quotedtext}
 @p{brk}
Don't do that, please. "Voting" with your coinbase should mean you actually do the extra validation required by p2sh, otherwise you're saying you support a feature when you really don't. @p{brk}