{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://real-life.org/rltp/v1/schemas/sealed-envelope.schema.json",
  "title": "RLTP Sealed Envelope (rltp-delivery@0.17)",
  "description": "Encrypted travel form per Delivery Contract section 5: fresh ephemeral X25519 per envelope, HKDF-SHA-256 (empty salt, info 'rltp/v1/seal'), AES-256-GCM with 128-bit tag and empty AAD. Plaintext is JCS(document), 1..65536 bytes; the document digest is computed over the plaintext, never the ciphertext. Shipped vector: vectors/seal.json.",
  "type": "object",
  "required": ["rkid", "epk", "nonce", "ciphertext"],
  "additionalProperties": false,
  "properties": {
    "rkid": {
      "type": "string",
      "description": "recipient key-agreement key identifier: the X25519 Multikey the envelope is sealed to ('z6LS' + 44 base58btc chars)",
      "pattern": "^z6LS[1-9A-HJ-NP-Za-km-z]{44}$"
    },
    "epk": {
      "type": "string",
      "description": "ephemeral X25519 public key, 32 raw bytes, base64url without padding (43 chars); fresh per envelope, never reused",
      "pattern": "^[A-Za-z0-9_-]{43}$"
    },
    "nonce": {
      "type": "string",
      "description": "96-bit CSPRNG nonce, base64url without padding (16 chars)",
      "pattern": "^[A-Za-z0-9_-]{16}$"
    },
    "ciphertext": {
      "type": "string",
      "description": "AES-256-GCM ciphertext including 128-bit tag, base64url without padding, CANONICAL lengths only (length mod 4 is never 1; non-zero trailing bits are rejected at parse). Minimum 23 chars (1-byte plaintext + 16-byte tag); maximum 87403 chars (65536 + 16 bytes). Tag-only values are structurally invalid.",
      "pattern": "^(?:[A-Za-z0-9_-]{4})*[A-Za-z0-9_-]{2,3}$|^(?:[A-Za-z0-9_-]{4})+$",
      "minLength": 23,
      "maxLength": 87403
    }
  }
}