Proof
Check a record
Every day-one record is a short text signed with the Sphaera record key. You can check one right here in your browser, or with any Ed25519 tool.
Record key
Ed25519, base58. Records sign their UTF-8 text, which starts with sphaera-record:
B5nx8MaV92GNjRRyKTuY8V4drpJie4EAcs7u1kjJjVmR
Daily root
Each UTC day's records are folded into one Merkle root over sha256: leaf = sha256(0x00 + record text), node = sha256(0x01 + smaller + larger).