Kudos A Peer-to-Peer Discussion System
Based on Social Voting Luca Matteis lmatteis@gmail.com

Social Voting
(online discussions)

Nothing decentralized exists for discussing
online using social voting. Central entities have control over what can be discussed. Could alter users reputation. Challenges for decentralized systems: Who keeps track of user's reputation? Where is information stored and retrieved?

distributed hash table peers blockchain
key key get(key) put(key, val)

Incentives • Similar to Bitcoin:
mine and get points. • Universal fixed amounts make it uneconomical to use for trading. • To earn points users post content that others are willing to upvote.

Transaction (vote): Input —(key)—> Output
A—(a)—>B C—(d)—>D D—(a)—>A B—(c)—>A B—(b)—>A B—(d)—>C C—(b)—>D A—(a)—>C C—(d)—>C D—(c)—>B 4 users: A, B, C, D 4 DHT keys: a, b, c, d block #300block #299block #298 points(user A) = Outputs(A) = 3 points(key b) = key(b) = 2

A—(a)—>B C—(d)—>D D—(a)—>A B—(c)—>A B—(b)—>A
B—(d)—>C C—(b)—>D A—(a)—>C C—(d)—>C D—(c)—>B 4 users: A, B, C, D 4 DHT keys: a, b, c, d block #300block #299block #298 Most relevant keys: a = 3 d = 3 b = 2 c = 2 DHT Transaction (vote): Input —(key)—> Output Keys in the latest block are fresher because they are pushed more often to the DHTpoints(user A) = Outputs(A) = 3 points(key b) = key(b) = 2

peer What's relevant lately? 1.
get most relevant keys from the blockchain keys: a: 30 points, b: 45 points distributed hash table 2. get() the keys from the DHT 3. push() the keys to keep them alive in the DHT

peer Publish content. Content has
a key = k and a value = "Hello World" 1. push(k, "Hello World") to the DHT distributed hash table 2. make a transaction (vote) with k inside and soon it will be mined in a block

Transactions universal fixed amount Problem:
same user might have several addresses 1EzwoH… 1AZyMz… 50 points They could send votes with specific key to themselves to promote their own content (key)

Transactions universal fixed amount (constant)
With universal fixed amounts, transactions are of an atomic value. 1EzwoH… 1AZyMz… To send 50 points, he now needs to break it into 50 transactions (with amount=1) 1E..0 1….. 1….. 1..N-1 1….N 1 point 1 point amount = 1

Transactions universal fixed amount Each
transaction also requires a fixed fee 1EzwoH… 1AZyMz… To send someone a point (a vote) it requires 2 points from the sender: 1 for the receiver, 1 for the miners. Sending 10 points to someone would require 10 addresses with at least 2 points each. Creating 10 addresses with 2 points each, would require 10 transactions of 4 points each, meaning 40 points. 1E..0 1….. 1….. 1..N-1 1….N 2 points (1 fee, 1 receiver) tx amount = 1 fee amount = 1

Keep alive Transactions in the
latest blocks are republished more frequently to the DHT to enable quicker response times. Intuition: latest content is more frequently fetched. higher republish ratelower republish rate This means old content might not be present in the DHT anymore. System only works well for latest content: it's not meant to function as a permanent storage system (although DHT keys will remain permanently in the blockchain).

Groups subscription Content can be
categorized under specific groups such as: sports, videos, politics, astronomy, etc. to enable creation of communities (subreddits). higher republish ratelower republish rate Users subscribe to specific groups and their republish rate is biased towards content they're subscribed to. Intuition: smaller communities might die off into old blocks, therefore subscribers can help store that content for longer periods of time in the DHT. Usera subscription = soccer

DHT structure • Hierarchical structure
of comments to enable discussion (replies/responses are nested). • Two types of content: posts and comments. • Store little information (limited amount of bytes needed for comments/posts). • Groups can be assigned to posts to categorize content and enable creation of communities. • Blockchain doesn't care about this at all (all it needs is a reference).

Use cases 45 128 119
1890 Decentralized reputation Freedom of speech Proof of what anybody said available in the blockchain Relevant content stands out