Proof of Trust is a consensus mechanism where users "stake" the trust they've earned in a network in order to verify cryptocurrency transactions.
In a proof of trust system, users will earn a virtual value called "trust" every time they acquire a role in the ecosystem.
A highly trusted node will be able to verify transactions that are of equal or lower value than the trust this user has accumulated.
A node with low trust will only be able to verify transactions lower than their equivalent value. How trust is converted into value and vice-versa depends on each implementation.
A practical example might help illustrate the concept.
COTI (Currency of the Internet) is a system where Proof of Trust is employed.
Users earn trust via a structure called TrustChain. In this specialized application of a blockchain, trust flows from transaction to transaction according to the value a node exercizes in the ecosystem according to the following illustration :
Here we see the roles and type of participation in COTI.
Each of these roles and types will earn the user a certain amount of trust.
Should a user attempt to defraud X amount of COTI Coins in the system, they would lose an equivalent amount of trust in a permanent fashion.
The fraud would be registered on the blockchain forever.
When trust were lost by attempting to defraud the system, the equivalent amount of COTI Coin would be converted from the lost trust, and the defrauded victim would be reimbursed.
Proof of Trust in COTI also employs Proof of Work in order to guarantee a minimum amount of work was performed by network participants.
The key factor here is to have a fair value to trust conversion routing that accurately gives the correct amount of value to each role/type of participation on the network.
We hope this brief intro to Proof of Trust has given you a better idea about this consensus mechanism.
Many innovative projects are researching alternatives to Proof of Work due to the immense energy consumption required by that consensus mechanism.
Proof of Trust is an alternative where a user's history on a network gains value with their participation on the network, attracting more users and more value to the network via incentives.
Trust is lost when a user tries to defraud the system.
The important factor in Proof of Trust networks is to maintain a fair conversion factor between trust and the network's unit of value (usually a cryptocurrency token or coin) so that trust can be adequately weighed in during the node selection process for block validation.