# Gavin Andresen
# 2011-10-07 12:41:26
# https://bitcointalk.org/index.php?topic=46538.msg561466#msg561466

RE: 0-confirmation OP_EVAL transactions: @p{par}

I think I'm doubly-wrong. @p{par}

OP_EVAL transactions are non-standard to old clients, so they are dropped before being added to the memory pool.  Old clients will not relay them, old miners that follow the IsStandard rules won't put them in blocks. @p{par}

When a transaction comes in that depends on a transaction that is not in the block chain or memory pool, it is shunted into the orphan transaction pool, and isn't listed by listtransactions or show up in the GUI until all of its inputs are satisfied. @p{par}

The risk would be a rogue miner putting invalid OP_EVAL transactions into blocks, which would trick old clients into showing transactions that depend on them as 0/ or 1/unconfirmed.  @p{par}

 @p{brk}
RE: "but bitcoin addresses are UGLY and the WRONG way to do it!" @p{par}

Okey dokey.  If I recall correctly, people were saying exactly the same thing about URLs 10 years ago (...google... @p{(link}yup@p{link)}). @p{par}

If your argument is OP_EVAL is possibly insecure... it seems to me it is @p{(bf}much@p{bf)} easier to reason about the security of OP_EVAL than to reason about the security of URI schemes or schemes for passing around a transaction to be signed or using SIGHASH_ANYONECANPAY. @p{par}

I agree that protocols for passing around either transactions or signatures are needed, I just don't think agreeing on what those protocols aught to be will happen anytime soon (how much you want to bet there will be a protocol buffers versus JSON debate that rages on for at least six months?) @p{par}

RE: writing up a full design doc: I've always admired the IETF's "rough consensus and running code" approach to standards-making, so I'll be happy to write up a full design doc after I've got running code.  Actually trying to IMPLEMENT multisignature transactions has taught me a whole lot about what will work in practice and what won't. @p{par}

 @p{brk}
Finally, to try (in vain, probably) to focus discussion:  The use cases I care about are: @p{par}

1. A user running bitcoin on a device that gets infected by malware. I want them to be able to subscribe to some service that will provide transaction confirmation for any outgoing bitcoin transactions above a certain amount per day (like my bank does with my ATM card). @p{par}

2. And I want them to be able to have a 'master wallet key' stored in physical form in their safe-deposit box so they can recover their wallet if they forget their passphrase or lose all their backups. @p{par}

OP_EVAL appeals to me because I can see EXACTLY how to make those use-cases work with minor variations to the infrastructure we have today for performing bitcoin payments. @p{brk}