Private Credentials
Ghost Protocol enables credentials that can be verified without being revealed, and that cannot be leaked because they are never stored.
The Problem with Traditional Credentials
When you prove your identity or qualifications today, you typically do one of the following:
Show the credential. You present a document, certificate, or token. The verifier sees the full credential, including information you may not want to share.
Rely on a database. The verifier queries a central database to confirm your status. This requires the database to exist, be available, and be trusted.
Trust an intermediary. A third party vouches for you. This requires trusting the intermediary and accepting their involvement in your transactions.
All of these approaches leak information. The credential is seen, the query is logged, or the intermediary learns about your activities.
The Ghost Protocol Approach
With Ghost Protocol, credentials work differently:
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Credential issuance. An authority issues you a credential by creating a commitment and giving you the secret.
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Credential holding. You hold the secret. The commitment exists on-chain, but no one knows it represents your credential.
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Credential verification. When you need to prove the credential, you generate a zero-knowledge proof that you know the secret to a valid commitment. The proof verifies without revealing which commitment is yours.
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Credential consumption. Depending on the use case, the credential may be consumed (one-time) or may support multiple proofs (reusable).
What This Changes
No visible credentials. Your credentials are not stored anywhere that can be searched, leaked, or hacked. They exist only as secrets in your possession.
Selective disclosure. You prove you have a credential without revealing which specific credential (among all issued) is yours.
No tracking. Verifications cannot be correlated. Each proof is independent and reveals nothing about your history.
Issuer independence. After issuance, the issuer has no ongoing role. They cannot revoke, track, or interfere with your credential use.
Categories of Use
Private credentials enable many categories of applications:
Age verification. Prove you are over a certain age without revealing your birthdate or identity.
Membership proof. Prove you belong to a group without revealing which specific member you are.
Qualification attestation. Prove you hold a certification without revealing your name or certification number.
Financial standing. Prove you meet a financial threshold without revealing your exact balance or account details.
The Design Space
Ghost Protocol credentials can be designed along several dimensions:
Reusable vs. one-time. Some credentials should be provable multiple times (e.g., age). Others should be single-use (e.g., a voting right).
Attributable vs. anonymous. Some credentials should be linkable to an identity on reveal. Others should be permanently anonymous.
Expiring vs. permanent. Some credentials should have time limits. Others should last indefinitely.
The underlying commitment model supports all of these designs. The specific choice depends on the application.
Limitations
Private credentials are powerful but not universal:
- They require someone to issue the credential in the first place
- They cannot prove negative statements (that you do not have a property)
- They consume the credential on reveal if one-time use is required
These limitations are inherent to the model, not implementation gaps.