[Bitcoin-development] On OP_RETURN in upcoming 0.9 release

[Mark Friedenbach]

Given our standardization on 128-bit security / 256-bit primitives, I
can't think of any crypto related data payload which requires more than
40 bytes. Even DER encoded compressed public keys will fit in there. A
signature won't fit, but why would you need one in there?

There's no need to design for 64-byte hashes, and the 80-char line
length comparison is a good point. As an Engineer I'd want to have a
little more room as a 32-byte hash or EC point + 8 bytes identifying
prefix data is the bare minimum, but it is also very important that we
send a message: This is for payment related applications like stealth
addresses only. Don't burden everybody by putting your junk on the block
chain.

On 02/24/2014 08:39 AM, Wladimir wrote:
> 
> On Mon, Feb 24, 2014 at 5:03 PM, Jeff Garzik <jgarzik at bitpay.com
> <mailto:jgarzik at bitpay.com>> wrote:
> 
>     A common IRC proposal seems to lean towards reducing that from 80.
>     I'll leave it to the crowd to argue about size from there. I do think
>     regular transactions should have the ability to include some metadata.
> 
> 
> I'd be in favor of bringing it down to 40 for 0.9.
> 
> That'd be enough for <8 byte header/identifier><32 byte hash>.
> 
> 80, as the standard line length, is almost asking for "insert your
> graffiti message here". I also see no need for 64 bytes hashes such as
> SHA512 in the context of bitcoin, as that only offers 256-bit security
> (at most) in the first place.
> 
> And if this is not abused, these kind of transactions become popular,
> and more space is really needed, the limit can always be increased in a
> future version.
> 
> Wladimir
> 
> 
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