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A Secure and Decentralized Network for Peer-to-Peer Advertising
BITFARI: A Secure and Decentralized Network for Peer-to-Peer Advertising – Light PAPER

Jordhy Ledesma, [email protected]
v0.1.2 Jun 2021

ABSTRACT. Bitfari Sits atop Bitcoin to create a civil network where users can publish, collaborate, self-organize, and pool resources all while acting pseudonymously. The Bitfari network allows businesses of any size to connect directly to consumers and form Impromptu commercial bonds to satisfy consumer needs in realtime with no middlemen involved.  

1. Introduction: Bitfari as the Internet of Places

Consider a system that ties all the screens in a city: screens from smartphones, desktop computers, electronic billboards, smart TVs, laptops, tablets, etc. This system is a new kind of social network that connects needs with solutions. An information brokerage system that dynamically feeds a potential solution to interested parties. Such a system could solve one of our most pressing problems: the world in which we live constantly requires our adaptation. How lovely would it be to have the world adapt to us? Surely it would feel like a heavenly breeze.

Bitfari is a system that deploys the concept of an adaptive matrix of blockchain connected screens to display contextual real-world ads and information systems at the command of the citizens. With Bitfari installed on your iPhone you could press a button and translate the entire city to your native language, for example. You could also block political ads, see relevant products without entering any store and, perhaps most importantly, place your own ads and calls for action allowing you to start a movement or recruit locals that can help you.

Most readers will naturally think about “Minority Report” ads, but Bitfari is exactly the opposite: ads placed by regular citizens, that don’t scan your face, don’t know your identity and don’t sell you stuff you don’t want. Bitfari connects you to other citizens by showing only the ads that you want to see, coming from people who share your interests. Blockchain technology makes this possible today.


2. Background

Bitfari was originally called Tellfari. The first prototype was shown at the University of Virginia in 2012. Subsequent research about adaptable cities was published that year in the paper “Best Buy: Investing in Language Learning”. That paper explored the economic benefits of providing personalized service in Spanish for Latino immigrants. Bitfari was later prototyped using blockchain technology and is now presented as an open-source Internet layer to enhance online and offline communications now that Bitcoin scaling solutions (such as Stacks 2.0) make possible to offer it to millions of consumers.

3. Network Elements: Screens, vScreens, Alter Egos, Channels, Social Oracles, Style Sets, Variables and the Disclosure Matrix

Screens and virtual screens are the most visible components of the network. This includes a set of physical and virtual screens that will house ads, content, and apps. Physical screens are conceived as inexpensive smart TVs that have, at a minimum a web browser and can point to an address and show web content.

Virtual screens are used as placeholders for AR style billboards, only reachable from smart glasses connected to the Bitfari network or augmented reality windshields in cars. The initial plan is to deploy vScreens with Bitfari’s Picasso release. Alter Ego is a login structure where the account identifier, a public key assigned to a user, a pseudonym, an avatar, a color, a hashed password and a place of origin are housed. For example:

alterEgo1 = {publicKey, ‘BoyGenius’, ‘avatar15’, ‘Red’, ‘eeb7048c69b088739908f5f5144cd1f5’, ‘New York’ }

When displaying this user’s identity in the ad space we can expect to see something along the lines of:

BoyGenius of New York we have 30% OFF Coupon for you! – and so on. Instead of a photo, the user gets to choose an avatar from a library. A color is also chosen to map the ad space that is targeting the use to his/her smartphone for maximum recall potential.

Channels include categories such as politics, shopping, food, erotica, religion, etc. This allows users to filter which ads they don’t want to see. We also use channels as an avenue for content segmentation, meaning offices, private residences, parks, beaches,

Style Sets include pre-approved fonts, vector images and photos that make possible the fast approval of basic ads. More complex ads go through the social oracle approval process.

Social Oracles can either be people or machines. A set of social oracles are chosen at random to evaluate an ad’s fitness for publication within a time-space-location. The number of social oracles chosen depends on the size, duration, channel and distribution of the ad.

Variables contain the essential elements for ad programmability. They can contain the alter ego, city, location, date, interests, likes, keywords and exploration lists of the user. Variables also store information regarding the weather, language of the ad, etc. A sample ad created with variables could look like:

Hey BoyGenius of New York! It’s raining, do you have an umbrella?



4. Network Operation

The steps to run the network are as follows:

4.1 Screen/vScreen dApp: Screens rotate ads and apps as their schedule shows.

4.2 User Auditing dApps + Social Oracles Validation: Ad placement is filtered by humans and machines for consensus to avoid fraud, reward good ads, punish bad ads and to ensure screen operators are aware of any ads that potentially break the law. Human auditors are paid a base bounty plus, sometimes, a random bounty akin to a “block reward”. 

4.3 Ad performance dApp: Ad performance metrics are broadcasted to its owners. A trail of ad performance is logged for each screen, providing advertisers with foot traffic data, history of reported fraud if any, ad price history, screen ad placement history, size, model, screen photos, live foot traffic photos, etc. There will be facilities right after launch to even see the screen via live video displaying your ad.

4.4 Ad creator dApp: Ads are created HTML5 and other standards. Images will use SVG, and are to be store in IPFS or a similar system. All images will undergo social approval prior to publication. Images used in community ads will be preapproved by the BitfariDAO governance process (essentially a biyearly voting process for token holders). Images used in agency ads will be not be posted pseudonymously but via a chain of approval containing trusted sources. Again, agency images will undergo auditing, unless the channel specifically forbids it. This modality is provided for private networks wishing to save some money and have full control over their screens.

4.5 Screen operators are paid after screen auditing (the screen is verified to exist, operating in normal condition and projecting in a location as specified in the app) and after an ad has exhausted an agreed upon period. Normally, this means operators are paid daily on or before 12:00 AM in the time zone configured for the area in which the screen has joined the network.

4.6 Screen dApp: Screen operators can choose to include apps or pause their screens. Operators can also include ads for their businesses in their screens at no cost to them.

5. Contextual Ads and Apps

Bitfari always displays the most appropriate ad according to the disclosed interests of pedestrians. Concretely, the summation of interests S contains the union set of interest keywords while SA contains the union set of scheduled ads for the screen in question. Bitfari matches this two by using ad keywords, ad copy and customer preferences.

6. Ad Booking, Review and Acceptance

Ad booking is determined by the advertiser. He or she selects the place, time and running conditions of the ad. However, auditors and social oracles will come in to certify the booking. Auditors are people, social oracles, machines. They work together to prevent fraud and keep screen operators out of trouble. While it is the responsibility of operators to review every ad, auditors can ease the burden by calling attention to certain issues. Spam, foul language, hate speech and the like will be automatically banned by social oracles (small social contracts tuned to the language and culture of every area).

For example, consider the language-social-oracle. This is a machine oracle containing a list of negative words and phrases for a given language. Ads are automatically dismissed by code running this social oracle on and off-chain.

The screen operator/ad-miner can configure a probability of consensus γ in order to reject or approve ads. The probability of consensus can vary due to many factors: political climate, governmental regime, ad space location, etc.

In this case the algorithm will simply reject proposed ads until the piece contains no negative words or phrases and a set of oracles has cleared the ad with a probability higher than or equal to γ. While this makes automatic ad booking and distribution feasible by adjusting γ for each area, we’ll simply call out poorly rated ads that at a minimum have clear the social oracle review process and let screen operators decide on whether to take the ad.

Regarding images, they are immutably stored on IPFS or a similar system. They can also come from a preapproved set. Images are always reviewed by real people before being placed in the system.

7. Placement and Other Fees

Fees are calculated using region, foot traffic figures for a given season, type of ad, duration, screen size, auditing costs, transaction fees and network maintenance fees. In some regions some government taxes will apply.

8. Human Review

While ads are booked and distributed automatically, social oracles are selected at random from a pool of application users in the area. These users will determine whether an ad is appropriate for their areas. The human mining portion of the transaction fee will be disbursed to them automatically. This human review process includes ad auditors, pre-auditors and screen reviewers. The review process occurs 24/7 with paid reviews occurring multiple times per day for each user.

Pre-auditors check ads and stock images before they are published and after machine review has cleared, auditing happens after the ad has been published but not widely distributed and screen review occurs after initial screen setup and after a screen issue is reported by a critical mass of customers or auditors. Auditing carries a cost and could require the deployment of thousands of auditors to review a single ad schedule for global distribution due to cultural, or geopolitical issues.

For additional reference regarding auditing and fraud prevention, please refer to our Fraud Prevention Whitepaper. 


At the discretion of the storefront or screen owner, an ad can be cancelled if it enters into conflict with the owner’s religion, personal convictions or if it’s considered detrimental in any way to his business or the immediate surroundings. Ad owners will be refunded the placement fees for the remainder of the duration in the ad’s schedule.

9. Virality and Ad Sharing

Depending on the area and channel, there will be a small time allocation for advertisers to be placed for free on the screens of their choosing if their ad first reaches a good auditing score and then receives good reviews by users.  Ads can also be shared on the platform as well as shared to other social networks. The aforementioned process creates the possibility of reaching something akin to virality but in the physical world. 

10. Hives, Daisy Chaining and Embellishments

Smart TVs and external monitors can be daisy chained or “hived” to create bigger ad spaces. This will result in higher earnings for screen operators. Ad space embellishments, useful decorations, transparent screens, etc will result in higher payment. These are evaluated based on the feedback of body of auditors which have visited the screen. 

11. Space Donation

The network will allocate a percentage of space time in order to provide free ad space to social interest causes as chosen by the governance polls. Screen operators shall be paid in full for these showings. 

12. Conclusion

We have proposed a system for decentralized global ad display and management. The solution will always work regardless of the presence of bad actors due to the economic incentives involved, machine filtering of spam and blatant ads and stakeholders’ ultimate decision regarding the fitness of the ad.

Screens work all at once with coordination provided by smart contracts. Regarding privacy, ad publishers do not need to be identified, since they are judged on the basis of the quality of the message they want to broadcast.



(1) Eades, Kenneth M.; Dickey, Keith; Ledesma, Jordhy; Frazier, Jennifer; Sider, Duane; Johnson, Melissa – Best Buy: Investing in Language Learning

(2) Mark Bonchek, Harvard Business Review – How Top Brands Pull Customers into Orbit

(3) Jamie Parfitt, 2012 – Citizen Advertising and the Transition Towards Consumer Collaboration

(4) Brand, J. (2013, March 5). Clarification of citizen advertising. (M. T. Choy, Interviewer)

(5) W. Feller, “An introduction to probability theory and its applications,” 1957.

(6) Satoshi Nakamoto, 2008 – Bitcoin: A Peer-to-peer Electronic Cash System. https://

(7) Nick Szabo – Formalizing and Securing Relationships on Public Networks relationships/

(8) Gonçalo Pestana and others – THEMIS: Towards a Decentralized Ad Platform with Reporting Integrity (Part 1)

(9) Thorsten Holz and others – The Dark Alleys of Madison Avenue: Understanding Malicious Advertisements

(10) Brave Software – Basic Attention Token (BAT) Whitepaper – Blockchain Based Digital Advertising



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