Descriptions of various terms used by Sismo
Fundamentally, Sismo revolves around data ownership. By using Sismo, users and applications alike can get the most out of their data. To achieve this vision, Sismo uses a combination of core products, underlying technology, and illustrative narratives. This article explains this terminology in order to give readers a clear understanding of Sismo.

Core Products

Sismo’s core products include the Data Vault, Sismo Connect, and ZK Badges. Descriptions of these core products can be found in the table below.
Data Vault
Sismo’s Data Vault stores accounts or attestations known as Data Sources. Pieces of data within Data Sources, represented as Data Gems, categorize users by elements of their digital identities.
Typically, a user’s experience with Sismo begins in the Data Vault. After aggregating their identity, users can then make provable claims about Data Gems they own which are subsequently verified by applications. The Data Vault is encrypted and only ever exists in its decrypted state on a user’s device.
Sismo Connect
Sismo Connect is a crypto-native single sign-on method (SSO). Once integrated, applications can request private, granular data from users, while users can authenticate and selectively reveal their data.
With Sismo Connect, applications privately authenticate users via a Vault Identifier or by revealing a Data Source directly. Meanwhile, users are in full control of the data they reveal to applications.

Classifying Data

Data is fundamental to Sismo and appears at multiple levels. Data is represented in Data Sources, Data Gems, and Data Groups. Descriptions of these terms can be found in the table below.
Data Source
Data Sources are sources of truth that range from web2 and web3 accounts to attestations and other credentials. Users add Data Sources to their Data Vault to store personal data and aggregate their identity.
Within Data Sources lies provable data, yet it is not bound to any account or attestation in the Data Vault. Valuable pieces of personal data can be dislodged from their associated Data Source and stashed away in the Data Vault.
Data Gem
The atomic pieces of data stored in a user’s Data Vault are characterized as Data Gems. Each Data Gem has an owner, value, and categorizes a user into a specific Data Group.
As Data Gems can be leveraged independently of their Data Source, they can be seen as fungible and account-agnostic within the confines of the Data Vault. Data Gems can be revealed without exposing the source of truth or associated owner via verifiable claims.
Data Group
Data Groups contain pieces of data that categorize users by similar characteristics. Users in the same Data Group can bring the same element of their identity to gated applications.
Users become members of Data Groups by owning Data Gems of the same category. For example, holders of NFTs in the same collection own a similar Data Gem and are thus in the same Data Group. The number of NFTs held by a particular user is represented by the Data Gem’s value.

Technical Terms

Sismo is ultimately a communication layer between a user’s sovereign data and applications. Descriptions of the underlying technology that facilitates this can be found in the table below.
Proving scheme
A proving scheme is a circuit in which users establish ownership of personal data. Proving schemes consist of provers and verifiers. Provers generate proofs for user claims that are authenticated by verifiers integrated into applications.
When users connect to applications via Sismo Connect or mint Badges, they participate in a proving scheme to verify ownership of Data Gems (i.e, personal data) in their Data Vault.
Users initiate proving schemes by making a claim about the data aggregated in their Data Vault. A claim states that a user owns a particular Data Gem over a certain value and thus belongs to a specific Data Group.
For example, an application may require a user to hold an NFT from a certain collection for access control. When connecting to the application with Sismo Connect, users claim to own at least one of the NFTs in question.
A proof is a cryptographic method of proving a given claim is true. Proofs are generated by provers after initiating a proving scheme inside the Data Vault.
Currently, all Sismo proving schemes utilize zero-knowledge proofs (ZKPs). ZKPs verify claims without revealing how they are true and facilitate Sismo’s privacy-preserving functionality.
Verifiers are one of the fundamental components of proving schemes. Developers can implement verifiers into their applications (on-chain or off-chain) by integrating Sismo Connect.
When integrated into applications, verifiers establish that user claims are true. They can be leveraged by applications for access control and reputation importation.
Once a claim has been verified by an in-app verifier, it is considered an attestation. Attestations are proven facts about a user’s digital identity.
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