Decentralized Storage in ZKID

Decentralized storage is a foundational component of ZKID’s architecture. Solana provides speed and execution, Bitcoin provides immutability, but neither chain is suited for storing large identity documents or credential metadata.

ZKID resolves this by using a hybrid decentralized storage model, optimized for:

• cost-efficiency

• permanence

• verifiability

• privacy

• cross-chain consistency

ZKID storage covers all identity-related data, including:

• DID Documents

• VC metadata

• ZK proof artifacts

• issuer signatures

• state snapshots for validators

Why ZKID uses decentralized storage

✅ 1. Efficiency

Storing full documents on-chain is not feasible. By storing only hashes on Solana, and documents off-chain:

• the blockchain remains lean

• the user retains data ownership

• large identity data is distributed optimally

✅ 2. Privacy

Full DID documents may contain:

• service endpoints

• public key rotation history

• VC references

• credential issuance metadata

Storing this encrypted off-chain preserves confidentiality.

✅ 3. Scalability

Identity systems scale linearly with users. Solana supports it, but permanent data must not inflate account state.

Externally attached, cryptographically linked storage solves this.

---

ZKID Storage Architecture

+-------------------------------+
| Bitcoin Anchor Layer          |
|  - Immutable State Roots      |
+-------------------------------+
            │
            ▼
+-------------------------------+
| Solana Smart Contract Layer   |
|  - Hash references            |
|  - DID mappings               |
|  - VC validity flags          |
+-------------------------------+
            │
            ▼
+---------------------------------------+
| Decentralized Storage Layer           |
|  - Arweave (permanent)                |
|  - IPFS (redundant)                   |
|  - Filecoin (pinned)                  |
|  - encryption optional                |
+---------------------------------------+
            │
            ▼
+-------------------------------+
| Client Layer                  |
|  - DID wallets                |
|  - VC holder apps             |
|  - dApps & verifiers          |
+-------------------------------+

---

Identity Storage Workflow (extended)

Step 1: DID Document Creation

Generated locally by the user:

• keys

• DID identifier

• metadata

• service endpoints

Stored temporarily in memory.

Step 2: Document Hashing

The client computes:

CID = SHA256(DID_Document)

This CID becomes the reference stored on-chain.

Step 3: Off-Chain Upload

Depending on configuration:

• Arweave → permanent

• IPFS → fast, distributed

• Filecoin → incentivized redundancy

Step 4: On-Chain Recording

Solana contract stores:

• CID

• timestamp

• owner address

• optional encryption reference

Step 5: Periodic Bitcoin Anchoring

Validators periodically submit a batched root of DIDs + CIDs.

---

Storage Format Example: DID Document JSON

{
  "id": "did:zkid:12ab34",
  "publicKeys": [
    {
      "id": "key-1",
      "type": "ed25519",
      "publicKeyBase58": "Cn2...8qz"
    }
  ],
  "service": [
    {
      "type": "Messaging",
      "endpoint": "https://relay.zkid.io"
    }
  ],
  "updated": "2025-06-30T19:21:00Z"
}

---

Smart Contract Example (Solana/Anchor)

#[account]
pub struct DidStorage {
    pub cid: [u8; 32],
    pub owner: Pubkey,
    pub created_at: i64,
}

pub fn store_document(ctx: Context<StoreDocument>, cid: [u8; 32]) -> Result<()> {
    let storage = &mut ctx.accounts.did_storage;
    storage.cid = cid;
    storage.owner = ctx.accounts.user.key();
    storage.created_at = Clock::get()?.unix_timestamp;
    Ok(())
}

---

Security & Redundancy Strategy

ZKID includes:

• multi-region Arweave redundancy

• optional encrypted Blob format

• automatic IPFS pinning

• periodic validation sweeps

• re-verification of CIDs vs stored content

Decentralized storage is not optional — it's essential.

ZKID uses:

• Solana (hashes + references)

• Arweave/Filecoin/IPFS (data)

• Bitcoin (finality & anchoring)

Result: Efficient, private, distributed user-owned identity storage.