Ethos has four major mechanisms that help us determine onchain credibility of crypto participants: Review, Vouch, Slash and Invite.

These mechanisms represent peer-to-peer interactions that help document what people say about each other, hold them accountable for their actions, and create a trusted environment.

Each mechanism is critical to how Ethos functions: Review and Vouch borrow from simple real-world primitives like “leave a review for someone” or “I’m going to back someone with money,” while Slash borrows from web3 primitives that we have in Proof-of-Stake. The most important of them all, however, is likely the most underappreciated: Invite. Joining Ethos requires an invitation, and inviting someone can have consequences for the inviter if the invitee proves untrustworthy.

Let’s take a peek at these four mechanisms to explain how each helps shape the Ethos onchain credibility score:

Reviews are the most simple form of peer signals we use in web2: Yelp, TrustPilot, Glassdoor, ZocDoc, WireCutter – even YouTube – are all filled with reviews we use to evaluate products, services and other people.

In Ethos, reviews are simple: mark the review as negative, neutral or positive and include a simple title and description. Any wallet or Twitter account can be reviewed, regardless of if they are also a user of Ethos. We see these reviews being used in a few different ways:

• You want to support a friend and show others that you back them? Leave them a positive review.

• You completed a transaction over-the-counter for Friend.Tech points and they followed through with their end of the deal? Leave them a positive review.

• Your favorite influencer or celebrity just pumped and then dumped a memecoin? Leave them a negative review.

These are simple signals that give us insight into interactions in the space: we can see who is interacting, the types of interactions that are happening, and how those interactions are going overall.

Reviews have minor effects on credibility score, but can compound over time. Reviews will be spam resistant in that a significant number of reviews from the same person in a short period of time will have diminishing returns on credibility.

Lastly, reviews in Ethos can become more valuable as we are able to weight them based on different things. For example:

• Similar to Chess ELO Scores, reviews that come from highly credible people for people with lower credibility scores have a bigger impact

• Users with low credibility scores have minimal impact to credibility score when reviewing people

• Every review has a built-in filter; upvoting and downvoting, which enables consensus to be driven about what reviews are helpful or not.

Vouching in Ethos is the highest signal to others that someone can be trusted. Similar to staking Ethereum to a validator, the act of vouching in Ethos is putting your money against someone’s name, signaling to the rest of participants that this person can be trusted.

Unlike reviews, which are sybil-tolerant and subject to spam, vouching adds an additional layer of economic security to the protocol. A user with a significant amount of vouched Ethereum against their name is measurably more credible than someone with a couple of positive reviews.

Vouching for someone has a meaningful impact on their credibility score, but the credibility score must be earned over time from continuous vouching as opposed to granted immediately.

Credibility scores can also be multiplied through the idea of “cooperation” and mutually vouching, where two parties vouch for each other. This is what is often referred to as “The Prisoner’s Dilemma” - where ultimately cooperation is the best outcome for everyone.

Of course, there will always be a time when you need to get your money back after vouching for someone. Within Ethos, when you remove a vouch, you will be prompted to label it as either 'Healthy'—indicating you still support the person—or 'Unhealthy'—indicating that the person has done something to cause you to remove your vouch. For example, if you are removing a vouch from someone simply to reallocate funds you might mark it as “Healthy”, but  if the person you vouched for pulled the rug on their project and you need to signal you don’t support that person anymore, you would mark it as “Unhealthy.”

Finally, it is important to know the Ethereum you vouch into Ethos is subject to the next mechanism, called Slashing. Your Ethereum vouched is only at risk if you step out of line and get Slashed, so don’t worry - your eth is not at risk if you vouched for someone else who launches a scam token.

Vouching for someone will have additional incentives that we aren’t quite ready to share - more on that closer to launch!

While vouching represents a more significant version of a “positive review,” slashing represents a more significant version of a “negative review.” In traditional Proof-of-Stake implementations, slashing is used to prevent validators (that operate on staked Ethereum.. like vouching!) from stepping out of line and approving transactions that are invalid. Slashing acts as a financial downside in staking and encourages consensus.

We’re bringing this idea to Ethos, where users will be able to suggest that other users be slashed.

If a user who is attempting to be credible by participating in Ethos and vouching for other users gets slashed, their Ethereum and social reputation is suddenly at risk. This will encourage participants to protect their credibility and, consequently, their capital by remaining upstanding community members.

For a slash to be proposed, the slashing party must produce a bond, or a minimum amount of Ethereum that will then be awarded at the end of the slashing period. This will initiate a process to determine consensus about the slashing: Was the person who initiated the slashing correct in promoting the event? Did the individual being slashed step out of line, or was this a baseless attempt to slash someone without justification?

Other Ethos users will be able to participate in driving consensus by voting on the outcome while the slashing event is live. Depending on the result, the Ethereum that was at stake is then split up in different ways:

• If the slashing is agreed upon, the person who was slashed will lose a percentage of their staked Ethereum in Ethos, and it is distributed back to who initiated the slashing and who participated in the voting.

• If the slashing is denied, the bond that was put up to initiate the slashing would then be distributed to the person who was attempted to be slashed and whoever participated in the voting.

We are fine tuning these details as we work through our implementation, so expect change and adaptation as we learn!

The last mechanism, Invite, is one of the most important parts of Ethos. Contributing to Ethos requires that you are invited to participate. To start, invitations are limited and exclusive to ensure a high level of accountability and credibility within Ethos.

Inviting another user has an important component that’s similar to the other mechanics: you create a bond with the person you invite, and both users' credibility scores impact one another’s for a limited period of time.

This encourages users to invite high quality people and discourages users from inviting bad actors or their own sybiled accounts. If you invite someone whose credibility score deteriorates quickly, that could negatively impact your own score as well.

Invitations allow us to retain scarcity, control population early, learn under sybil-constrained circumstances, and keep the contributions to Ethos high. Invitations are so important that who invited you is prominently displayed on your profile card for everyone to see. It acts as a shield, a barrier of defense for all the other mechanisms.

Reviews, Vouches, Slashes and Invites are the primitives of Ethos. Together, they enable us to create a measurable, onchain credibility score to benefit all crypto participants and drive ethical and trustworthy actions across web3.