NFT-Encrypted Identity
Your identity is a digital badge that lives on the Solana blockchain — it cannot be stolen, transferred, or faked. When you log in, you prove you hold the badge by signing a unique one-time challenge. We also confirm the badge is still live on-chain before granting access. Your data is locked with a key only your wallet can generate — ZKey never holds it. To remove someone, an admin destroys their badge on-chain. Access is gone permanently. No grace period.
Soulbound pNFT with Deny-All Rule Set
A Metaplex Programmable NFT (pNFT) is minted to the user's Solana wallet at onboarding. The NFT is bound to a custom Authorization Rule Set that denies all transfer operations — Wallet-to-Wallet, Sale, Delegate, LockedTransfer — making it permanently non-transferable. The only permitted action is an authority-only burn using a PubkeyMatch rule tied to the mint authority. This makes the NFT a true soulbound credential: it cannot be sold, gifted, or moved — only destroyed.
// Rule Set (mpl-token-auth-rules v2)
operations: {
'Transfer:WalletToWallet': notV2(passV2()), // deny
'Transfer:Owner': notV2(passV2()), // deny
'Delegate:Sale': notV2(passV2()), // deny
'Burn:Holder': pubkeyMatchV2('Authority', mintAuthority), // admin only
}Challenge–Response Auth Flow
On login, the server generates a cryptographically random 32-byte nonce (stored in Redis with a 5-minute TTL) and returns it to the client. The client signs the message `ZKey Auth: <nonce>` with their Solana wallet private key using Ed25519. The server verifies the signature with TweetNaCl and simultaneously checks the user's token account on-chain to confirm the soulbound NFT is still present and active. Both checks must pass. Once verified, a session token is issued and cached in Redis for 1 hour.
// Verification
const msg = new TextEncoder().encode(`ZKey Auth: ${nonce}`);
const valid = nacl.sign.detached.verify(msg, sig, pubkeyBytes);
const tokenAccount = await getAccount(connection, ata);
assert(tokenAccount.amount === 1n);Wallet-Derived Encryption (AES-256-GCM + HKDF)
Encrypted records stored in ZKey use keys derived from the user's wallet signature — never from a server-side secret. The client signs a deterministic derivation message, feeds the signature into HKDF-SHA256 to produce a 256-bit Data Encryption Key (DEK), then encrypts data with AES-256-GCM. The DEK is wrapped (encrypted) with each authorized NFT holder's wallet-derived key and stored alongside the ciphertext. The server stores only ciphertext and wrapped keys — it never sees the plaintext DEK.
// Client-side only (never on server)
const sig = await wallet.signMessage(deriveMsg);
const dek = await hkdf(sig, salt, 'ZKey-DEK-v1', 32);
const { ct, iv } = await aesGcmEncrypt(dek, plaintext);
const wrapped = await aesGcmEncrypt(holderKey, dek);Threshold Decryption (Shamir Secret Sharing)
For high-security records, the DEK is split into N shares using Shamir's Secret Sharing. Each authorized NFT holder receives one encrypted share. Decryption requires any K-of-N holders to cooperate (threshold). The server coordinates a threshold session — collecting blinded share contributions from K holders — but the final DEK reconstruction happens exclusively on the client side. The server never holds enough shares to reconstruct the secret alone.
Instant Revocation via Admin Burn
When a user's access needs to be revoked, an admin triggers a burn transaction using the mint authority's keypair. The pNFT is permanently destroyed on-chain via the Metaplex burnV1 instruction. All wrapped keys and shares associated with that mint address are immediately deleted from the database. Any subsequent auth attempt fails the on-chain ownership check — the wallet no longer holds the credential. No grace period, no token blacklist needed.
Audit Trail
Every significant NFT auth action is recorded in an immutable audit log: nonce generation, signature verification, session creation/expiry, mint, burn, record creation, key wrapping, and threshold session events. Logs capture wallet address, mint address, IP, user-agent, success/failure, and timestamp — providing a complete forensic record for compliance.
