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Frequently asked questions

A system or network that allows entities to securely request and store a proven permission, to send an email to another entity inside a decentralized peer-to-peer blockchain. We also call this permission the Double-Opt-in procedure, as it is requested by European data protection regulations (GDPR). In future Doichain will be used as a spam protection system.

If Alice wants to store the permission, that she is allowed to email Bob, she requests this via her own Doichain dApp and node instance. Typically Alice is an e-commerce company, shop or another marketing related company. The request is automatically broadcasted to Bob’s Doichain node inside an unconfirmed Doichain transaction. In case Bob doesn’t have or want a Doichain node, the node of an either self-configured trustable third party is used (DNS TXT value) or if that isn’t available either too, a trustable fall back node of is chosen instead. What ever trusted node was receiving the email permission request, the transaction will immediately trigger the nodes dApp to send out the Double Opt-in request email to Bob via SMTP. Bob can now confirm the request via a HTTP-link to Bob’s dApp. Bob’s dApp will store the confirmation inside his version of the Doichain, by also signing it with his own private key.

A single Double Opt-in costs 0.02 DOI. It is planned to upgrade the DOI in future, to become a so called SmartCoin. That way the price of storing a Double Opt-in will be bound to the Euro. 1 DOI has a nominal value of 1 Euro, so the cost will be 0.02 Euro, in order to write a DOI to the blockchain. Having this functionality ensures stability in calculation of costs for companies, who need a stable service price for their business model.

The decentralized nature of blockchain ensures the proof-of-existence of a given Double Opt-in permission. Permissions can not be faked, since only the entity, who gives the permission, can sign it from its own version of the blockchain.

In fact no personal data is written inside Doichain neither in plain text nor in encrypted form. This wouldn’t comply with European data protection regulations. Alice generates a hash inside of her dApp and links it to her version of Bob’s contact information in her private local database, which is part of the dApp. The hash is saved together with Alice’s & Bob’s signature inside Doichain, to confirm a valid Double Opt-in.

These coins were mined by the core team during the first weeks of the Doichain launch. They are reserved for the Doichain non-profit organisation, to ensure further development and implementations, which are visible in the roadmap.

Every email service provider (ESP) can install a so called SMTP filter. It’s scanning all incoming emails and can decide, if the email gets accepted or rejected. Emails which have a proven Doichain-SMTP-header (which includes the address of the entry inside Doichain and the public key of Bob) can proof, that the sender of this email has a valid Double Opt-in signature. In such a case this email would be automatically regarded as non-spam. We can imagine, that in future big players like Google and Hotmail implement the Doichain system, in order to fight spam. Consequently the Doichain will become de facto standard.

At the time of evaluation for suitable crypto currency technologies (we didn’t wanted to reinvent the wheel) the Namecoin blockchain seemed to be is the perfect base layer for storing Double Opt-ins. During implementation of the first prototype we realized, that in order to speed up the processing of a Double-Opt-in request, we would have to modify Namecoin. So we forked Namecoin into Doicoin. Furthermore the cost of storing the permission and the price of NMC (Namecoin) was already too high, to ensure a stable business models, which use atomic Double Opt-ins.

As soon as Alice executed the HTTP-POST to the Doichain-dApp REST interface, the addresses of sender and recipient get immediately broadcasted to the Doichain network. Bob’s Doichain node is receiving the transaction and sends out the email via SMTP. This whole procedure takes usually about 5-10 seconds.

First of all and most importantly we want to implement and upgrade Doichain to a classic MultiSig workflow – how to request, confirm and sign a Double Opt-in. The existing prototype right now still needs a lot of care regarding the setup, configuration and necessary security checks. Documentation and software tests need to be written for the Doichain dApp and Doichain node. The price for storing a Double Opt-in needs to be coupled with the average price of a DOI in EUR and many other little things in terms of marketing and a freely convertible crypto currency, that need to be solved. But especially we want to have a convenient Mobile App for Android and iOS, so the end user can manage the given permissions directly from one place.