This article is about an unused payment protocol. For the online wallet service by a similar name, see GreenAddress.
Green addresses was a proposed use of special trusted ECDSA keypairs that to indicate the origin of funds to a recipient. Assuming the recipient trusts the operator of the keypair to not attempt a double spend, the recipient may treat the funds as confirmed the moment they arrive. This proposal is generally considered a bad idea and not advisable to implement.
As an example, assume website Z accepts incoming Bitcoin payments, but also trusts the green address published by Mt. Gox. Customer C wants to withdraw funds from Mt. Gox and send them to a payment address of website Z. A customer who does a withdrawal from Mt. Gox could click the use green address checkbox, which will result in the payment being sent to the "green address" derived from the special keypair as an intermediate step before forwarding the payment to site Z. Site Z can confirm that the payment passed through Mt. Gox's keypair and trust the payment as confirmed immediately, since it knows that the only party who could potentially perform an attack to reverse the payment is Mt. Gox.
The concept originated on the Bitcoin Talk forum in 2011 and was discussed in two threads. Since then, it was implemented by Instawallet and Mt. Gox, both of which have since been compromised and closed.
Confusion between wallet/controller and owner
Bitcoin signatures do not imply any particular legal origin of bitcoins, and when the signature is used to imply some origin, it seems to perpetuate this myth.
In order to actually use green addresses, it is necessary to create an extra transaction to the special ECDSA keypair before then forwarding it on to its final destination.
- What Are Green Addresses Q&A on StackExchange