> For the complete documentation index, see [llms.txt](https://docs.zkid.digital/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zkid.digital/zkid-foundation/zkid-layer-technical-breakdown.md).

# ZKID Layer Technical Breakdown

### System Overview

ZKID follows a modular, multi-layer architecture:

1. **Identity Layer**
2. **Credential Layer**
3. **ZK Verification Layer**
4. **Application Layer**

***

### 1. Identity Layer

Focused on:

* DID creation
* key management
* document resolution
* Bitcoin anchoring
* decentralized reference points

Pseudocode for DID creation:

```rust
fn generate_did() -> DID {
    let keypair = secp256k1_generate();
    let did = format!("did:zkid:{}", hash(keypair.public));
    DID { did, keypair }
}
```

***

### 2. Credential Layer

Handles:

* issuance
* revocation
* validation
* metadata referencing

Credentials remain primarily off-chain to ensure scalability.

Smart contract reference example (Solana / Anchor style):

```rust
pub struct CredentialReference {
    pub did: Pubkey,
    pub storage_hash: [u8; 32],
    pub issuer: Pubkey,
    pub valid_until: i64,
}
```

***

### 3. ZK Verification Layer

This layer processes:

* zkSNARK-based proofs
* membership proofs
* age proofs
* custom ZK circuits

Example ZK circuit pseudocode:

```
// prove user is over 18 without revealing birthdate

def zk_age_proof(birth_year, current_year):
    assert(current_year - birth_year >= 18)
```

In real implementation, this becomes a constraint system (R1CS or Plonk).

***

### 4. Application Layer

Applications integrate:

* credential requests
* DID verification
* ZK proofs
* permissioned access
* reputation scoring
* session-based authentication

Example flow:

```
User -> DID
DID -> VC
VC -> ZKProof
ZKProof -> Access Granted
```

***

### ✅ Identity Anchoring Workflow (Expanded)

#### Step 1: User creates DID

Locally generated to ensure privacy.

#### Step 2: Hashing

The DID Document hash is computed.

#### Step 3: Bitcoin anchoring

Batch updates follow a structure like:

```
commitment_root = merkleRoot(DID_updates)
OP_RETURN(commitment_root)
```

#### Step 4: Solana reference

Solana contracts reference the anchored state:

```rust
pub struct AnchoredDIDState {
    pub did: Pubkey,
    pub btc_commitment: [u8; 32],
    pub last_update_slot: u64,
}
```

***

### ✅ Credential Flow (Expanded)

#### Issuance

Issuer signs VC:

```
signature = Sign(issuer_private_key, credential_data)
```

#### Storage

Credential stored on Arweave:

```
arweave://cred/0x123abc...
```

#### Verification

Apps query:

```
VerifySignature(issuer_public_key, credential, signature)
```

Optional: run ZK proof:

```
VerifyZKProof(credential, zk_proof) -> true/false
```

***

### ✅ Data Synchronization (Expanded)

Validators maintain:

* DID update logs
* revocation registries
* proof validity
* hash commitments
* BTC anchoring intervals
* time-based checkpoints

Reward logic sketch:

```rust
fn distribute_rewards(validators, epoch_rewards) {
    let total_stake: u64 = validators.iter().map(|v| v.stake).sum();
    for v in validators {
        v.reward += epoch_rewards * (v.stake / total_stake);
    }
}
```