Developing 'Private Social Networks' with Onchain Keys

Summary: Private social networks can now ship enterprise-grade E2EE, seamless passkey logins, auditable permissions, and anonymous-but-accountable posts by anchoring MLS group keys, delegated signers, and ZK membership proofs on Ethereum L2s. Below is a pragmatic blueprint—down to contract standards, gas costs, and rollout metrics—that 7Block Labs uses to deliver secure, compliant, and scalable private networks.

Hook: The specific headache you’re wrestling with right now

• Your roadmap says “invite‑only communities with E2EE, SSO, and compliant archiving”—but your stack can’t reconcile passkeys, key rotation, and group encryption across web and mobile.
• Your PMs want Apple/Android-native login (passkeys), legal wants selective retention, security needs auditable key ceremonies, and growth needs pseudonymous posting without sockpuppets. Meanwhile, your wallet team is stuck debating seed phrases vs. embedded wallets.
• And every week you delay, moderation debt grows, invite churn rises, and the board asks why “private social” is still a slide, not a SKU.

Agitate: What failure looks like by Q2–Q3 2026

• Missed deadlines as you rebuild auth twice: first for WebAuthn, then again to make it “onchain”—because your L2 doesn’t verify P‑256 signatures natively. EIP‑7951 brings a P‑256 precompile with verification semantics and a clear gas schedule (P256VERIFY at 0x100; ~6,900 gas), but if you don’t plan for it now, you’ll ship brittle shims you’ll rip out later. (eips.ethereum.org)
• Group messaging ships without forward secrecy or post‑compromise security; your “private” rooms leak when one admin is phished. MLS (RFC 9420 protocol + RFC 9750 architecture) is the modern baseline, and it’s already rolling into RCS for hundreds of millions of devices—your users will expect it. (datatracker.ietf.org)
• “Anonymous mode” becomes a spam magnet. Without ZK proof‑of‑membership (Semaphore v4) and nullifier‑scoped rate limits, you’ll be forced to reintroduce full identity—killing trust and engagement. (docs.semaphore.pse.dev)
• Invite flows expose your graph. ERC‑5564 stealth addresses and the ERC‑6538 registry exist to deliver non‑interactive, scannable, private invitations; ignore them and you’ll leak who invited whom on day one. (eips.ethereum.org)

Solve: 7Block Labs’ methodology to ship “private social” with onchain keys—without crypto theater We deliver in four concurrent workstreams—Identity, Groups, Content, and Compliance—then land a go-to-market slice with measurable metrics.

1. Identity and login: WebAuthn passkeys, onchain-verifiable

• Why now: Passkeys achieve materially higher sign‑in success and lower latency (93% success; ~73% faster), which directly boosts conversion through your invite funnel. Pair that UX with onchain verifiability so your apps, bots, and contracts speak the same trust language. (fidoalliance.org)
• How we implement:
  • WebAuthn/Passkeys (P‑256) as the primary credential; signatures verified on L2 using the P‑256 precompile (EIP‑7951), eliminating custodial seed phrases while keeping hardware-backed auth (Secure Enclave, Android Keystore, FIDO2 keys). We map the P256VERIFY interface (160‑byte input; 32‑byte “1” on success) and enforce r/s and point bounds at the precompile layer. (eips.ethereum.org)
  • For EOAs already in the wild, we enable one‑time “smart” capabilities via EIP‑7702 (tx type 4) so legacy addresses can batch actions or accept gas sponsorship without migrating users to new wallets. This complements 4337 stacks; it doesn’t replace them. (eip.info)
  • Counterfactual signers from day one using ERC‑6492, so you can verify signatures for accounts not yet deployed and keep invite flows snappy. (eips.ethereum.org)
• Outcomes you can measure:
  • Conversion: +20–30% lift at “Join” due to passkey success rates; sign-in time cut from ~31s to ~8.5s; fewer help‑desk tickets around password resets. (fidoalliance.org)

1. Group security: MLS for E2EE + onchain signer governance

• Baseline: We standardize on IETF MLS (RFC 9420 protocol, RFC 9750 architecture) for group key establishment with forward secrecy and post‑compromise security. This is the same class of crypto RCS is adopting; it’s battle‑tested for large groups. (datatracker.ietf.org)
• Onchain anchors (not payloads):
  • We write group metadata commitments (MLS epoch, roster hash, cipher suite) to an L2. This gives you provable state without posting ciphertext onchain.
  • We govern “who can post” via delegated signers anchored to an identity registry:
    • Example: Farcaster’s pattern—custody address on OP Mainnet controls Ed25519 signer keys registered onchain in a Key Registry. Apps post through these delegated signers; custody can rotate or revoke signers. We adapt this pattern for your network (custody could be a smart account or enterprise KMS). (docs.neynar.com)
• Practical controls:
  • Short‑lived poster keys (7–30 days) tied to device trust, rotated automatically on MLS epoch change.
  • Role‑based write scopes (channels, caps, rate limits) evaluated in your smart account module or via 7702‑authorized code during a transaction.

1. Private invitations and discoverability—without graph leakage

• Implement ERC‑5564 stealth addresses so inviters generate one‑time, unlinkable recipient addresses (derived from recipient’s published stealth meta‑address). Recipients scan via view tags; spending keys remain private. For lookup, we use ERC‑6538 registry entries per “entity,” set via EIP‑712/EIP‑1271 signatures. Result: your invite ledger is auditable, but outsiders can’t correlate recipients. (eips.ethereum.org)
• This pairs well with MLS pre‑shared secrets: invites hand off both a stealth spend right (onchain) and an encrypted MLS Welcome (offchain), enabling instant E2EE on first join.

1. Anonymous‑but‑accountable posting with ZK membership

• Use Semaphore v4 so users can “prove membership once per scope” without doxxing themselves. Nullifiers prevent double‑posts; moderators can rate‑limit by scope without deanonymizing members. For votes and sensitive surveys, we deploy MACI, giving you receipt‑free anti‑collusion governance. (docs.semaphore.pse.dev)
• Engineering note: We verify proofs onchain only for decisions that must be settled there; everything else verifies offchain for speed, with periodic commitments.

1. Storage, DA, and performance: keep secrets offchain, proofs onchain

• Message payloads and media never hit the chain—only authenticated commitments and key metadata do.
• For rollup costs, we batch channel/epoch commitments into EIP‑4844 blobs; when your scale grows, PeerDAS (EIP‑7594) reduces network overhead by sampling availability rather than downloading every blob. That’s how you keep DA cheap without sacrificing integrity. (eips.ethereum.org)
• Architecture options we productionize:
  • Encrypted object storage (S3/GCS/Azure) with MLS‑rotated content keys; hash commitments on L2.
  • IPFS/Ceramic/Arweave for public discoverability wrappers; binary remains encrypted end‑to‑end.
  • Optional threshold re‑encryption (PRE) to feed compliance archives without exposing live keys.

1. Compliance, procurement, and business continuity (the things that kill deals if you ignore them)

• RTO/RPO: We define directory recovery and signer rotations that survive device loss and SOC events. Custody may live in HSM/KMS; poster keys are disposable and auto‑rotated.
• DSAR and data minimization: PII lives offchain, encrypted under MLS group keys and device passkeys. Moderation only sees content where policy requires; otherwise we prove “membership/eligibility” instead of leaking identity.
• Archiving: Optional export to WORM storage with capture keys held under legal hold policies; mapping from MLS epochs to retention events is onchain and auditable.

Who this article is for—and the keywords you actually search for

• Target audience: Heads of Product and Security at:
  • Collaboration suites launching invite‑only communities
  • Consumer social apps adding “private circles”
  • B2B platforms building partner networks with E2EE
• Your required keywords (woven above and below, not buzzwords):
  • WebAuthn P‑256 wallets; EIP‑7951 P256VERIFY; EIP‑7702 delegated code; ERC‑6492 counterfactual signatures; ERC‑5564 stealth addresses + view tags; ERC‑6538 meta‑address registry; MLS RFC 9420/9750; Farcaster custody + delegated signers on OP Mainnet; Semaphore v4 nullifiers; MACI for receipt‑free votes; EIP‑4844 blobs; EIP‑7594 PeerDAS.

Practical example 1: Invite‑only founder network with private discovery

• Goal: Founders can invite partners privately; posts are E2EE; anonymous Q&A within verified groups; no seed phrases.
• Flow:
  1. A founder publishes a stealth meta‑address via ERC‑6538. 7Block Labs’ service posts the registry entry with an EIP‑712 signature from their custody account. (eips.ethereum.org)
  2. An inviter calls generateStealthAddress() with the recipient’s meta‑address, writes the announcer event (with view tag) and includes a short‑lived MLS Welcome encrypted to the stealth address’ key. The recipient’s wallet scans via the view tag and derives the spend key locally. (eips.ethereum.org)
  3. Recipients authenticate with passkeys; their device registers a delegated poster key (Ed25519) on the group’s Key Registry. If they lose a device, custody rotates the signer; group MLS updates the epoch, and clients rekey automatically. (docs.neynar.com)
  4. For “Ask Me Anything” threads, users post with a Semaphore proof scoped to threadId; the app enforces one post per identity per thread without revealing who posted. (docs.semaphore.pse.dev)
• Why it works:
  • No graph leakage (stealth + view tags), instant E2EE (MLS Welcome), no seeds (passkeys + P‑256 precompile), and spam resistance without deanonymization (Semaphore).

Practical example 2: Enterprise partner portal with SSO and legal archiving

• Goal: Partners sign in with enterprise SSO; content is E2EE; legal can archive; performance is predictable at scale.
• Flow:
  1. Employees authenticate via your IdP (OIDC). On first use, the app issues a platform-bound passkey, anchors the device’s P‑256 pubkey on L2 (or links it to a smart account), and records an onchain authorization for session code execution via EIP‑7702 for specific operations (e.g., batch “post + pin + tip”). (eip.info)
  2. MLS manages channel keys; admin revocation rotates epochs; devices update seamlessly.
  3. Compliance connector re‑encrypts selected channels into archival keys (offchain PRE), indexing MLS epochs to retention SLAs. Only commitment hashes land on L2, reducing exposure during audits.
  4. Quarterly rotation triggers: signer TTLs expire; devices renew; audit log contains (epoch, rosterHash, signerId) tuples for each write grant, verifiable against the L2 anchor.

Practical example 3: Creator communities with “frames” and delegated posting

• Goal: Let companion apps and bots post on behalf of a user without seizing the keys.
• Flow:
  1. User’s custody (EOA or smart account) adds a delegated poster signer; the app posts via hubs that verify signatures map to onchain-registered keys (pattern proven in Farcaster). Custody can revoke the app-specific signer at any time. (docs.neynar.com)
  2. For ephemeral “pop-up” rooms, the app creates MLS subgroups; poster keys are scope‑limited, auto-expiring with the room.

Emerging best practices we’ve road-tested (2025–2026)

• Identity:
  • Prefer passkeys as the primary factor; do not fall back to seed phrases for consumer flows. Map device keys to L2 verifiers (EIP‑7951) to keep verification cheap and universal. Expect ~6,900 gas per verify. Money phrase: “Passwordless UX with onchain verifiability.” (eips.ethereum.org)
  • Use EIP‑7702 selectively: batch multi‑call “post + reactions + follow” and support paymasters for gas sponsorship on high‑value actions. (eip.info)
• Groups:
  • Make MLS your default; rotate on admin changes and at fixed intervals; expose epoch in your APIs; persist the (groupId, epoch, rosterHash, cipherSuite) commitment on L2 for replay detection and audits. (datatracker.ietf.org)
• Privacy and invites:
  • Adopt ERC‑5564 + ERC‑6538 for invite issuance and scanning. Use view tags aggressively to keep client scanning cheap. Publish org-wide meta‑addresses under an “entity” entry, not per user, when HR/legal requires pre‑approval. Money phrase: “Private invitations without social-graph leakage.” (eips.ethereum.org)
• Anonymous posting:
  • Scope Semaphore nullifiers to channel/thread, not tenant; hard‑rate‑limit by scope to deter Sybil floods; verify proofs offchain, commit aggregates onchain. (docs.semaphore.pse.dev)
• DA and cost control:
  • Aggregate write events and epoch changes into EIP‑4844 blobs; for very high throughput, plan to leverage PeerDAS (EIP‑7594) on mainnet/L2 to keep bandwidth sane. Money phrase: “Auditable state, negligible DA cost.” (eips.ethereum.org)

GTM: metrics we sign up to move (and how we forecast them)

• Top‑of‑funnel conversion
  • Passkeys deliver materially higher sign‑in success (~93%) and faster auth (~8.5s vs. ~31s), which we model as a +20–30% improvement in successful joins from invite. We’ll A/B passkeys‑first vs. password‑first during your pilot. (fidoalliance.org)
• Content velocity with safety
  • Delegated poster keys (revocable, scoped) yield a measurable increase in daily posts while keeping abuse reversible; we track signer churn and revocation MTTD/MTTR from the L2 anchors inspired by Farcaster’s custody/signer model. (docs.neynar.com)
• Privacy‑preserving engagement
  • Semaphore‑backed “anonymous questions” show higher participation without multi‑account spam; we report unique‑nullifier counts per thread and verification failure rates over time. (docs.semaphore.pse.dev)
• Infra cost and reliability
  • DA cost per 10k messages via 4844 blobs vs. calldata; blob inclusion SLOs; reorg sensitivity. We include PeerDAS readiness in the runbook for networks that opt in. (eips.ethereum.org)

Specifications snapshot (what we ship, quickly)

• Identity and Wallet
  • Primary auth: WebAuthn passkeys (P‑256)
  • Onchain verification: EIP‑7951 P256VERIFY; EIP‑7702 for batched/sponsored calls; ERC‑6492 for counterfactual contract signers (eips.ethereum.org)
• Groups and Permissions
  • E2EE: MLS (RFC 9420), architecture per RFC 9750; short‑lived poster keys mapped to devices; onchain group state commitments (datatracker.ietf.org)
• Privacy and Invitations
  • Stealth addresses: ERC‑5564 (view tags; non‑interactive); meta‑address registry: ERC‑6538 (EIP‑712/EIP‑1271 support) (eips.ethereum.org)
• Anonymous Posting
  • ZK membership: Semaphore v4; optional receipt‑free voting: MACI (docs.semaphore.pse.dev)
• Data Availability & Cost
  • Commitments: EIP‑4844 blobs; future‑proof with EIP‑7594 PeerDAS on networks where available (eips.ethereum.org)

How we work with your team (and where each service fits)

• Architecture and build:
  • We design, implement, and harden the core with our custom web3 development services and custom blockchain development services, including MLS integration, signer registries, and EIP‑7702 flows.
  • Smart contract modules for invites, signer governance, and proof verification via our smart contract development team.
• Security and audit:
  • Pre‑production threat modeling, key ceremony design, and code reviews via our security audit services.
• Integration and rollout:
  • IdP/SSO, KMS/HSM, and data‑layer wiring through our blockchain integration practice.
  • If your network spans L2s or appchains, our cross‑chain solutions development team handles interop and data‑consistency guarantees.
• Front‑end and app layer:
  • We ship your MVP client with our dApp development offering so users feel “consumer‑grade” from day one.
• Go‑to‑market acceleration:
  • For teams raising or launching, we package a compliance‑ready demo and KPI model via our fundraising advisory.

Brief, in‑depth details you can hand to engineering today

• Passkeys on L2: With EIP‑7951, passkey signatures (r,s + Qx,Qy) are verified natively. Budget ~6,900 gas per verify. Add a malleability check at the app layer if you mirror NIST semantics. Pair with EIP‑7702 for batched ops (e.g., “post + tip + notify”) to keep UX one‑tap. (eips.ethereum.org)
• Delegated posting (Farcaster‑style): Custody (EOA or smart account) authorizes Ed25519 poster keys; hubs accept posts signed by registered keys; revocation and rotation are onchain. This yields safe “Login with X + Post from Y app” without key sprawl. (docs.neynar.com)
• Private invites at scale: Publish org or user stealth meta‑addresses (ERC‑6538); send invites via ERC‑5564 Announcer with view tags; recipients scan quickly, no interactive handshake required. You get private distribution with provable delivery. (eips.ethereum.org)
• Anonymous Q&A that can’t be farmed: Semaphore v4 proofs bound to thread scope prevent re‑use; you can set per‑scope rate limits and still keep identities private. Use MACI if you need bribery‑resistant tallies. (docs.semaphore.pse.dev)
• DA cost planning: Post only commitments and key events to chain; aggregate into EIP‑4844 blobs. As throughput grows, PeerDAS lets nodes sample availability, keeping your infra bill and sync times in check. (eips.ethereum.org)

Why 7Block Labs

• We bridge Solidity, ZK, and MLS with procurement‑grade deliverables: key ceremonies, BCP/RTO, compliance hooks, and executive‑level metrics dashboards. You get “consumer UX, enterprise control, provable privacy”—not just a wallet bolted on a chat app.

Personalized CTA If you’re the Head of Product or Security owning a Q2–Q3 2026 milestone for “private communities with E2EE and passkeys,” book a 45‑minute Architecture Review with our core team this week. We’ll map your IdP, choose your L2 (and EIP‑7951 availability), design your MLS + delegated‑signer topology, and give you a 30‑day pilot plan with KPIs (join‑rate lift, DA cost/10k msgs, revocation MTTR). Reply with “MLS‑Onchain, <your company>” and your target launch date—let’s make the deadline real.

References (select standards and sources cited inline)

• EIP‑7951 P‑256 precompile (verification semantics, gas): eips.ethereum.org. (eips.ethereum.org)
• EIP‑7702 delegated code for EOAs: eip.info. (eip.info)
• ERC‑6492 counterfactual signature validation: eips.ethereum.org. (eips.ethereum.org)
• ERC‑5564 stealth addresses (view tags; announcer): eips.ethereum.org. (eips.ethereum.org)
• ERC‑6538 stealth meta‑address registry: eips.ethereum.org. (eips.ethereum.org)
• MLS protocol (RFC 9420) and architecture (RFC 9750); RCS adoption: IETF. (datatracker.ietf.org)
• Farcaster custody + delegated signers on OP Mainnet: Neynar docs, dTech explainer, Farcaster protocol discussion. (docs.neynar.com)
• Passkey business impact (success rate, login time): FIDO Alliance Passkey Index (2025). (fidoalliance.org)
• EIP‑4844 blobs and EIP‑7594 PeerDAS for DA scaling: eips.ethereum.org. (eips.ethereum.org)