Elydora Epoch Root (EER)

The EER is a periodic Merkle root that anchors all operations within a time window into a single verifiable hash, signed by Elydora.

Structure

Field	Type	Required	Description
epoch_id	string	Yes	Unique identifier for this epoch.
org_id	string	Yes	Organization identifier.
start_time	number	Yes	Unix millisecond start of the epoch window.
end_time	number	Yes	Unix millisecond end of the epoch window.
leaf_count	number	Yes	Number of operations included in this epoch.
root_hash	string	Yes	SHA-256 Merkle root of all operation hashes in the epoch.
hash_alg	string	Yes	Hash algorithm. Currently "sha256".
signature_by_elydora	string	Yes	Ed25519 signature by Elydora over the epoch root.

Example EER

json

{
  "epoch_id": "0195f2c8-4d6e-7f8a-9b0c-1d2e3f4a5b6c",
  "org_id": "org_acme",
  "start_time": 1772287200000,
  "end_time": 1772287500000,
  "leaf_count": 1247,
  "root_hash": "<base64url Merkle root>",
  "hash_alg": "sha256",
  "signature_by_elydora": "<base64url Ed25519 signature>"
}

Merkle Tree Construction

The Merkle tree is built from the chain hashes of all operations received during the epoch window:

Leaves are the chain_hash values, sorted in ascending order.
Internal nodes are SHA-256 over the raw bytes of the two child hashes.
If the leaf count is odd, the last leaf is duplicated to complete the tree.

Verification

To verify that an operation is included in an epoch:

Call POST /v1/operations/:operation_id/verify; checks.merkle is true once an epoch covers the operation
Fetch the epoch with GET /v1/epochs/:epoch_id to read root_hash, leaf_count, the time window, and the RFC 3161 anchor when present

The signed EER stays in Elydora storage. The API returns the epoch record without signature_by_elydora.

Epoch Timing

Epochs close every 5 minutes. The epoch boundary uses the server receive time, not the client issued_at.