Independent decode
We decode the exact bytes being signed, including nested Safe, MultiSend and smart-account calls, instead of trusting what a compromised UI shows.
For exchanges, funds and treasuries
An independent second signature for your hot wallets
Bybit and Binance both lost billions to one signature that did something different from what everyone believed. The Co-Signer is the check your signing system cannot skip.
Live simulation
Every transaction is executed against the latest block first. You see the real asset movements and approvals before anything is signed.
Attack-pattern rules
Blocks 7702 delegations to unlisted contracts, revocation-proof authorization batches, multisig delegatecalls, blind signatures and unlimited approvals.
Limits and time-locks
Per-transaction hold and block thresholds and rolling 24-hour velocity limits. Large outflows wait for a second human.
Signed attestations
Every decision is signed with Ed25519 and bound to a SHA-256 of the request. It expires in 5 minutes. Your signer verifies before it signs.
Audit trail and alerts
Every evaluation is logged with its reasons and attestation, and streamed to your security team in real time.
Integration
One call before you sign
POST /api/v1/evaluate
Authorization: Bearer cg_live_…
{ "chain": "ethereum", "from": "0xHotWallet", "to": "0xRecipient",
"value": "250000000000000000000", "data": "0x" }
→ { "decision": "HOLD",
"reasons": [{ "decision": "HOLD", "title": "Value above review threshold (10)" }],
"simulation": { "status": "success", "changes": [{ "direction": "out", "amount": "250", "symbol": "ETH" }] },
"attestation": { "payload": { "decision": "HOLD", "requestHash": "…", "expiresAt": 1793330000 },
"signature": "…", "algorithm": "Ed25519" } }
FAQ
Frequently asked questions
How does the Co-Signer integrate with MPC, HSM or multisig setups?
Your signing service calls
POST /api/v1/evaluate with the unsigned request and signs only if it receives an ALLOW or WARN attestation that verifies against CryptGuard's Ed25519 public key, matches the request hash and is not expired. It works with Fireblocks-style policy webhooks, Safe signer bots, custom MPC nodes and HSM workflows.What does the policy control?
Behaviour for EIP-7702 delegations, multisig DELEGATECALL, unlimited approvals, unknown functions and blind signatures; per-transaction hold and block thresholds; rolling 24-hour velocity limits per sender; allowlists (optionally enforced) and blocklists; and live simulation before deciding.
Would it have stopped the Binance hack?
Under the default policy, the delegation of a hot wallet to a contract not on the allowlist is blocked, and so is a batch of pre-signed authorizations for future nonces. A sweep of the full balance would also exceed per-transaction and velocity limits. The signing system would never have received a valid attestation.
What happens if CryptGuard is unavailable?
You choose. Most customers fail closed for transfers above a threshold and fail open for routine low-value operations. Enterprise deployments can run the engine on-premises next to the signer.
Put a second signature on your hot wallets
Business starts at $499/month with the full Co-Signer API. Enterprise adds volume pricing, on-prem deployment and incident response.