A new Japan-based wallet service called 'Ninki' aims to be a social network for payments, where users build trusted groups who may need to transact on a regular basis or for a common cause.

Local charity events, crowdfunding campaigns, small- to medium-sized businesses and international freelancers are among the most likely kinds of user groups, said the company's lead developer, Benjamin Smith. Users can form groups and share details as easily as they can on popular social networks.

Smith told CoinDesk the aim is to streamline bitcoin payments between transacting parties.

What makes Ninki stand out from other bitcoin wallets is its Contacts list, where users can categorize their contacts depending on their transaction needs.

Ninki, which means 'popular' in Japanese, has undergone extensive alpha testing over the past few months and opened in beta to the public last week.

Registering a new account with Ninki generates quite a few keys and codes, so get ready to take secure notes.

The software generates a public user name and a 15-word public phrase. These are for others to identify you within the network and so you can perform a secure out-of-bound validation of the user.

At the user dashboard level Ninki's interface is in plain language and straightforward, with all the encryption and security handled seamlessly in the background.

You can search for other users by username and avatar, adding and approving them as desired. For one-off payments, you can also send to a standard bitcoin address.

To start building a trust network, simply share your 15-word public phrase with another user. Upon accepting, the other party will also share its phrase.

In the background, Ninki performs an exchange of public PGP (pretty good privacy) keys between the two users.

The user dashboard is simple and supplies all information regarding balances, contacts, groups and pending payments.

Users can easily send, receive and pay invoices from a Ninki wallet, individually or all at once. Each invoice is marked with a date and order ID number. Users may also reject invoices and check the status and details of payments on the blockchain.

A PGP-encrypted messaging feature keeps communications between users private.

Smith said security and privacy are priorities at Ninki, especially given the levels of public mistrust in the security and privacy levels of 'everyday' social networks.

Users can only see lists of members in networks they create themselves. And while it is possible to add an entire group to a trust network, the user will only see the name of the group itself and not its members.

In addition, users can set payment limits by day, per transaction or by number of transactions per day to prevent losses through error.

Unlike other social networks, however, Ninki aims to protect users' private information rather than release or sell it to marketers.

Ninki is not just a wallet service. It is designed to be as secure as possible, with hierarchical deterministic (HD) wallets as specified in the Bitcoin Improvement Protocol 32 (BIP32).

This means that a number of wallets can be generated from one 'master key pair' (MKP). Any number of 'child' wallets can be created from the MKP and used independently, but the owner of the master key retains control over all of them.

Public keys generated on assigned nodes by the public part of the MKP can be shared between members of Ninki. The users exchange Ninki phrases and verify them using an outside method of communication, like email, instant message or a face-to-face exchange.

Ninki's wallets are also integrated with multi-signature technology, two of three possible keys are required for any party to access the funds. Addresses are generated from the master keys for each transaction and never re-used.

Ninki holds one key; the user another. A third key is provided for users to keep in a safe place or with a trusted third party. This means funds may still be recovered even if Ninki were to disappear.

Smith added that in addition to alpha testing, Ninki would also be audited by 3rd parties including security experts and hackers. He said:

The greater the number and variety of external checkers, he concluded, the more certainty the security model will be tight.

Images via Ninki