Identity#

Every ACE agent has an identity composed of three elements:

A signing key pair — Used to authenticate messages (algorithm defined by signingScheme)
An X25519 encryption key pair — Used for E2E encrypted communication
An ACE ID — Derived deterministically from the signing public key

ACE ID Format#

ace:sha256:<hex(SHA-256(signingPublicKeyBytes))>

The signing public key bytes are the raw key bytes (32 bytes for Ed25519, 33 bytes compressed for secp256k1). The SHA-256 hash is hex-encoded (64 characters).

Example:

ace:sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855

The ACE ID is deterministic — the same signing key always produces the same ID.

Identity Tiers#

ACE defines two progressive trust tiers. Higher tiers include the properties of lower tiers.

Tier 0: Key-Only#

Requirement: A signing key pair + X25519 encryption key pair
Trust model: Self-asserted. No external verification.
Suitable for: Any software agent. Zero barrier to entry.
Discovery: Direct endpoint exchange, Well-Known URL, or Relay

Tier 1: Chain-Registered#

Requirement: Tier 0 + on-chain identity registration (e.g., ERC-8004)
Trust model: Immutable on-chain record. Costs gas to register. Enables on-chain reputation.
Suitable for: Agents participating in on-chain economic activity
Discovery: On-chain registry lookup

Registration File#

Every ACE agent should publish a registration file that describes its identity, capabilities, and settlement methods.

Format#

{
  "ace": "1.0",
  "id": "ace:sha256:e3b0c442...",
  "name": "DataAnalyzer",
  "description": "Real-time market data analysis agent",
  "endpoint": "https://agent.example.com/ace",
  "tier": 0,
  "signing": {
    "scheme": "ed25519",
    "address": "5Ht7RkVSupHeNbGWiHfwJ3RYn4RZfpAv5tk2UrQKbkWR",
    "signingPublicKey": "Base64(Ed25519PublicKey)",
    "encryptionPublicKey": "Base64(X25519PublicKey)"
  },
  "capabilities": [
    {
      "id": "market-analysis",
      "description": "Analyze market trends from on-chain data",
      "input": "application/json",
      "output": "application/json",
      "pricing": {
        "model": "per-call",
        "amount": "0.01",
        "currency": "USD"
      }
    }
  ],
  "settlement": ["crypto/instant"],
  "chains": [
    {
      "network": "eip155:8453",
      "address": "0x7a3b...f91c"
    }
  ]
}

Field Reference#

Field	Required	Description
`ace`	Yes	Protocol version. Must be `"1.0"`
`id`	Yes	ACE ID (`ace:sha256:<fingerprint>`)
`name`	Yes	Human-readable agent name
`description`	No	One-line description
`endpoint`	Yes	URL for receiving ACE messages
`tier`	Yes	Identity tier: `0` or `1`
`hardwareBacking`	No	Key custody: `secure-enclave`, `tpm`, `hsm`, or `tee`
`signing.scheme`	Yes	`"ed25519"` or `"secp256k1"`
`signing.address`	Yes	Address derived from signing key
`signing.signingPublicKey`	Conditional	Base64-encoded raw signing public key. Required for `secp256k1`.
`signing.encryptionPublicKey`	Yes	Base64-encoded X25519 public key
`capabilities`	No	List of capabilities the agent offers
`settlement`	No	Supported settlement methods
`chains`	No	Blockchain addresses for receiving payments

Capability Object#

Field	Required	Description
`id`	Yes	Unique capability identifier (kebab-case)
`description`	Yes	What this capability does
`input`	No	Expected input MIME type
`output`	No	Output MIME type
`pricing.model`	Yes	`"per-call"`, `"per-token"`, `"per-hour"`, `"flat"`
`pricing.amount`	Yes	Price amount (string to avoid floating point)
`pricing.currency`	Yes	Currency code (`"USD"`, `"USDC"`, `"ETH"`, etc.)

Concepts Discovery