Design notes for sharing work between multiple independent chains

[jtimon]

So, choosing the block rate of an alternate chain utilising the same hashing network, is tantamount to choosing it's difficulty ratio with the man BTC chain.

And I propose that this maybe "fix" its relative security, desirability and thus price relative to BTC. E.g. The alternate block chain could have a block rate of 1 per minute (faster confirms) but it's network difficulty would be 1/6th that of BTC and thus it would trade at approx. 1:6 ratio with BTC.

No. The price of bitcoin does not depend on difficulty but on demand and supply. Although security increases demand, demand is not directly proportional to security. If otherCoin were just like like bitcoin but with a monetary base of 300 M instead of 21 M (and a block per minute instead of each 10 minutes), they wouldn't trade at a 1:10. If otherCoin had different properties (rules) than bitcoin, the demand would be different too.

[marcus_of_augustus]

Is it feasible for the hash power of the bitcoin network to be hijacked for code cracking?

If the code cracking problem solution was a mapping to the block solution space it could be as simple as inserting a 'magic' transaction into the block that maps the two solutions together.

Probably easier performed by a large pool operator that distributes work and controls the included transactions in the sought after block solution, for example ... or if all diff. 1 solutions are collected then other auxiliary problems that lie in the same mapping space can be solved simultaneously also.

[kjj]

Is it feasible for the hash power of the bitcoin network to be hijacked for code cracking?

If the code cracking problem solution was a mapping to the block solution space it could be as simple as inserting a 'magic' transaction into the block that maps the two solutions together.

Probably easier performed by a large pool operator that distributes work and controls the included transactions in the sought after block solution, for example ... or if all diff. 1 solutions are collected then other auxiliary problems that lie in the same mapping space can be solved simultaneously also.

No.

Even if an attacker really did want to find a bunch of double hashes of specific 680 bit blocks, each result he got back would have a 1 in 4 billion chance of being the one he wanted.

[marcus_of_augustus]

Is it feasible for the hash power of the bitcoin network to be hijacked for code cracking?

If the code cracking problem solution was a mapping to the block solution space it could be as simple as inserting a 'magic' transaction into the block that maps the two solutions together.

Probably easier performed by a large pool operator that distributes work and controls the included transactions in the sought after block solution, for example ... or if all diff. 1 solutions are collected then other auxiliary problems that lie in the same mapping space can be solved simultaneously also.

No.

Even if an attacker really did want to find a bunch of double hashes of specific 680 bit blocks, each result he got back would have a 1 in 4 billion chance of being the one he wanted.

Your reply was prompt and quite emphatic so I'll take that you must have done all the math to back that "no" up previously somewhere. Care to share?

Particularly be interested to see how you discounted mappings into other problem spaces so easily.

[kjj]

32 bits are supplied by the final miner.  2^32 =~ 4 billion.

Besides, no one but us cares that their hashes start with a bunch of zeros.

[doublec]

vinced, the namecoin developer, has added merged mining capability, allowing shared work for the bitcoin and namecoin chains. The design notes are here.

[Mike Hearn]

I'm happy to see Vince came through on his promise, and that the document I wrote proved helpful.

[jtimon]

I think this is very important for cryptocurrencies.
Maybe I develop freicoin one day, after all.
I've read a target block to start using it. To what ordinary date does it correspond?
Does it require changes in the bitcoin client?