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= "an open source project whose goal is to make online naming and identity management more secure and user-centered".



By Chelsea​ ​Barabas, Neha​ ​Narula and Ethan​ ​Zuckerman:

"Blockstack is an open source project whose goal is to make online naming and identity management more secure and user-centered by reimagining user credentials, DNS, certificate authorities, and public key infrastructure for the Internet. Similar to public key infrastructure systems, their goal is to provide a way for users to “own their own identity” outside of a mega-platform like Google or Facebook, giving an alternative way of verifying identity and authenticity. Using Blockstack, an author associates a public key with their username of choice, which can then be used to verify that documents associated with that name were produced by that person. The author can include any relevant identifying information as the value (like his website or profile) and then (assuming his private key isn’t compromised) can make changes associated with that name in a way that cannot be forged without undermining the Bitcoin blockchain. This is done by cryptographically signing the hash (which serves as a unique, digital “fingerprint”) of each new version of the website–the hash can be cross checked to verify its consistency with the website’s latest version, and the cryptographic signature cannot be forged unless the keys are compromised. The author gives the actual URL or website to the verifier out of band."


By Chelsea​ ​Barabas, Neha​ ​Narula and Ethan​ ​Zuckerman:

"Blockstack is implemented as a layer for storing name/value pairs built on top of the Bitcoin blockchain, by registering Blockstack IDs. Blockstack uses Bitcoin’s blockchain to act as a tamper-resistant record of ordered operations, stored in Bitcoin transactions. Users issue two transactions to reserve a name–first a pre-order 90 transaction, which obfuscates the name being reserved but proves that the user was first, and then a register transaction, which completes reserving the name and makes the registration publicly visible. This is done to avoid front running–if everyone could see the name being registered before it was confirmed, a sneaky party might try to claim it first, or might use that information to undermine the user. Both of these transactions must appear on the Bitcoin blockchain, and so might take up to an hour or longer to confirm.

Once a name is registered, the owner of the private key used to sign the transaction registering that name then has control over that name’s value; the user can use their private key to make verifiable, signed changes to content, also in the form of Bitcoin transactions. For example, if Jane Doe decides to create a Blockstack username, ‘’, she could register that name in Blockstack, and others could see that was only done by someone with Jane’s private key (presumably Jane herself). She could then change the content that username points to, for example by updating her profile. Blockstack is designed to separate the storage and agreement of operations on the name/value pairs (like create, update, or delete) from the storage of the actual data being modified and stored. Users can point to content stored in a variety of places–Dropbox, Amazon web Services, IPFS, or their own website–by signing the location of the content (the URL).

Other users can read the Bitcoin blockchain to find the Blockstack-specific transactions, and check the operations on a username to determine its final value. For example, Bob might be trying to read the latest updates from Jane. He sees some information online that says that Jane stores her content on her website,, but he is not sure if this is really the Jane he is looking for. Bob knows that the Jane he is interested in has a username of ‘’ in Blockstack. He can read the Bitcoin blockchain to find the Blockstack transaction where Jane registered ‘’.

Then Bob could continue reading the Bitcoin blockchain to find the latest transaction signed with that registered public key to see where Jane stores her content, and validate that it really is by checking the signed URL. Theoretically, this could enable users to manage their own personal space on the internet for publishing–Jane can change the location of her content at any time simply by issuing a new Bitcoin transaction, and Bob can find and validate the change by reading the Bitcoin blockchain. In addition, Blockstack would also like to make their usernames usable as a single sign-on identity to login and federate user content across other platforms. The system could enable publishing competitors to more easily bootstrap new services since they could plug into existing, authenticated identities. But for all its promise, Blockstack may face challenges in assimilating into mainstream use on the web based on our three integration criteria: user adoption, developer opt-in and business viability. User adoption is probably the most challenging area for the Blockstack community to contend with. Prior efforts to support federated identity, such as OpenID, have gained traction only with very niche user bases. At its core, the limited adoption of independent identity systems like OpenID is tied to issues of demand. The average user doesn’t see the need for secure identity and thus isn’t interested in learning more about independently controlled identity solutions in order to adopt them.

As security researchers Whitten and Tygar argue, “People do not generally sit down at their computers wanting to manage their security; rather, they want to send email, browse web pages, or download software, and they want security in place to protect them while they do those things... Designers of user interfaces for security should not assume that users will be motivated to read manuals or to go looking for security controls that are designed to be unobtrusive.” Offering integration with a decentralized identity system is probably not enough of a differentiator to motivate users to put forth the effort to learn how its security tools work. When evaluating Blockstack’s potential as a mass identity solution, we must ask whether or not it offers additional benefits over these prior efforts, and if it effectively addresses the usability challenges that other systems have struggled to overcome in the past. It is possible, however, that Blockstack could find itself adopted as an essential component of another, very compelling system.

The Blockstack developers have been very intentional about the design of their system in order to address these challenges. Perhaps the biggest sticking point for Blockstack’s usability is related to its dependency on public key cryptography. Historically, strong cryptography has been very challenging for average users to deploy. For example, work evaluating the usability of PGP, perhaps the most well-known 92 public key directory to date, has shown that there is a lot of misunderstanding among users about how public key cryptography works and how to use it effectively. This 93 leads to serious use errors (i.e. accidently exposing secret keys) that nullify the overall security of the system. In order for the decentralized vision of the Blockstack system to work, the average user must either develop a coherent working model of how public key cryptography works, or designers must create intuitive user interfaces that enable average users to effectively manage their private keys.

In light of these challenges, the Blockstack team has made user experience design for private key management one of their top priorities. These design choices illustrate some of the important trade-offs that developers face when building decentralized systems that are also user-friendly. Technically, the most “decentralized” version of Blockstack would require users to download and validate the entire Bitcoin blockchain (currently around 120 GB) in order to validate the location of a friend’s content. This is impractical, given the amount of disk space the Bitcoin blockchain takes, and the technical know-how required to independently manage one’s own Blockstack and Bitcoin nodes.

Instead, Blockstack has mapped their cryptographic processes directly onto the familiar username and password procedures that users are already familiar with, and are utilizing third party providers. Today, new Blockstack users can register an identity via a registrar service like, which manages private keys for users and provides the familiar username/password login interface. Using, a user creates a password that encrypts a generated private key. The user is provided with a backup file that can be used to restore and reset their password in the event that he forgets his password.

Although the encrypted private keys are stored on Onename’s servers, this configuration is arguably more secure than the traditional username/password approach, because the Onename servers do not have direct access to the private keys. The user needs to decrypt the private key before issuing any update or transfer to the account. Therefore, Onename cannot act maliciously on behalf of the user. At the same time, the Onename model suffers from some of the same security problems as the traditional username/password model -- if Jane’s Onename password is compromised, for example via a phishing email, the attacker can still take over the account and make changes -- for example by creating a new website and attaching it to Jane’s Blockstack ID in order to post embarrassing content.

In the future, the Blockstack developers aim to eliminate passwords from their process altogether. This could happen in a couple of different ways. First, name registrars that build on top of Blockstack could develop alternative methods for managing private keys. Second, Blockstack is working to develop a client that supports a two-factor authentication process that would require authorization from multiple devices (i.e. the user’s laptop and mobile phone). Ideally, users would be able to authorize login requests with a simple click of a button, indicating their consent, without the need to remember additional information, such as a password or private key. Even if passwords were eliminated, however, the initial setup and recovery processes of putting private keys on their devices could prove quite challenging for everyday users. Blockstack is in the process of building a browser with a built-in wallet and built-in private key management that would enable a more seamless experience upon downloading. Of course, getting people to adopt a specialized browser to use your software is far from simple–developers have long bemoaned the challenges of getting users to download the latest version of the browser they already use, much less adopt an entirely new one. The Blockstack team will need to think carefully about how they roll out an effective adoption strategy for their specialized browser. Right now, they are focusing on a “Blockstack installer,” which upgrades existing browsers like Chrome and Safari, enabling users to access Blockstack from their default browsers.

The Blockstack project must also consider how to help users recover when their private keys are compromised, for example when they lose a device on which the private keys are stored. Traditional identity management providers accomplish this by providing a way for users to prove their identity, and then the identity management provider will reset their password. In​ ​a​ ​decentralized​ ​system,​ ​there​ ​is​ ​no​ ​authority who​ ​can​ ​perform​ ​a​ ​reset.​ A related decentralized identity solution in development for the Ethereum blockchain, UPort, has a scheme to do this by letting a user designate “friends” who can perform the reset for them. It remains to be seen whether this works in practice. There are many outstanding challenges–for example, if many users are compromised at once, as has happened with the Sony and Target hacks, a user may not have any friends left with available accounts to help.

The Blockstack developers are currently considering a multiple signature (aka “multi-sig”) scheme for achieving this goal, whereby a selected subset of a user’s family and friends would cooperate to reset one’s password on their behalf. In the coming years, issues related to key recovery and compromised accounts will remain important questions, ones that Blockstack will have to thoroughly contend with if their system is ever to achieve mass adoption." (


By Chelsea​ ​Barabas, Neha​ ​Narula and Ethan​ ​Zuckerman:

"Today Blockstack supports over 4,000 contributing members in its open source community and has registered over 70,000 domain names. The open source code is maintained by Blockstack Inc., a company which recently announced that it raised $4 million in funding from venture capital firms like Union Square Ventures and the Digital Currency Group. It will be interesting to see how this organizational structure will shape Blockstack’s prospects of adoption as an open standard."