Copay depends on Bitcore Wallet Service (BWS) for blockchain information, networking and copayer synchronization. BWS can be run within minutes or you can use a public instance. Switch between BWS instances is very simple and can be done with a click from Copay. BWS also allows Copay to interoperate with others wallet like Bitcore-Wallet CLI https://github.com/bitpay/bitcore-wallet.
Alternativelly, public BWS instances (like `https://bws.bitpay.com`) can be used.
To install it go to `chrome://extensions/` in your Chrome browser and ensure you have the 'developer mode' option enabled in the settings. Then click on "Load unpacked chrome extension" and choose the directory mentioned above.
*Copay* uses standart gettext PO files for tranlations. It is currently translated to spanish, japanese, french, german and portuguese thank to community contributions. See https://github.com/bitpay/copay/pull/2880 as an example pull request for adding translations.
*Copay* implements a multisig wallet using [p2sh](https://en.bitcoin.it/wiki/Pay_to_script_hash) addresses. It supports multiple wallet, with with its own configuration, such as 3-of-5 (3 required signatures from 5 participant peers) or 2-of-3. To create a multisig wallet shared between multiple participants, *Copay* requires the extended public keys of all the wallet participants. Those public keys are then incorporated into the wallet configuration and combined to generate a payment address where funds can be sent into the wallet. Conversely, each participant manages their own private key and that private key is never transmitted anywhere.
To unlock a payment and spend the wallet's funds, a quorum of participant signatures must be collected and assembled in the transaction. The funds cannot be spent without at least the minimum number of signatures required by the wallet configuration (2 of 3, 3 of 5, 6 of 6, etc). Once a transaction proposal is created, the proposal is distributed among the wallet participants for each to sign the transaction locally. Once the transaction is signed, the last signing participant will broadcast the transaction to the Bitcoin network.
*Copay* also implements [BIP32](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki) to generate new addresses for peers. The public key that each participant contributes to the wallet is a BIP32 extended public key. As additional public keys are needed for wallet operations (to produce new addresses to receive payments into the wallet, for example) new public keys can be derived from the participants' original extended public keys. Once again, it's important to stress that each participant keeps their own private keys locally - private keys are not shared - and are used to sign transaction proposals to make payments from the shared wallet.
For more information regarding how addresses are generated using this procedure, see: [Structure for Deterministic P2SH Multisignature Wallets](https://github.com/maraoz/bips/blob/master/bip-NNNN.mediawiki).
Copay uses the powerful and feature-rich [Bitcore](https://github.com/bitpay/bitcore) Javascript library for Bitcoin-related functions. Bitcore should be built this way:
Copay currently supports [BIP70 (Payment Protocol)](https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki), with the following limitations:
* Only one output is allowed. Payment requests that are more that one output are not supported.
* Only standard Pay-to-pubkeyhash and Pay-to-scripthash scripts are supported (on payment requests). Other script types will cause the entire payment request to be rejected.
