Are there already several ways to do "smart contracts" with cryptocurrencies?

Question

I have heard a lot of "buzz" about Ethereum, but apparently its 1.0 version won't be released for a while yet.

I have heard a lot of talk about "smart contracts" from people who admire Szabo, but I haven't seen many implementations.

I notice that Ripple lists "contracts" under "future" features, which seems to imply that they are not ready for use yet.

https://ripple.com/wiki/Main_Page

The one implementation I have seen is at :

http://erights.org/

Are there any other, more popular ways to implement "smart contracts" that are already in use?

Thanks

Answer 1

There is Orisi.org - you can read the whitepaper here Orisi.org/distributed oracles whitepaper, and run an example Timelock contract here.

The differences between distributed oracles/Orisi and Ethereum are:

• Orisi works on top of Bitcoin, so there are no other currencies inbetween
• oracles can reference external inputs, so you can create a contract that finalizes based on weather/currency prices, or even mechanical turk
• it's available today
• on the other hand, it has a different trust mechanism than Ethereum - oracles are supposed to be run by trusted independent parties. So, instead of proof of work, you have a proof of identity.

You can also read this blogpost by one of the bitcoin core devs: bit-thereum. It explains why m of n oracles might be a good solution for contracts.

Answer 2

I think that multi signature can be used to implement smart contracts, meaning that 2 or more signatures are needed to confirm the transaction for it to go through. E.g. a signature from the buyer and seller. I am not very sure but it's probably worth reading.