Block Header
A block header is what the block hash commits to; on chain 2800 every 32nd header since block 13,014,000 also binds a post-quantum certificate digest.
A block header is the compact record at the top of every block: the hash of the parent block, the roots that commit to state and transactions, a timestamp, and a field called extraData that consensus protocols use for their own bookkeeping. The block hash is computed from the header, so whatever sits inside the hashed portion is fixed for good: change one byte and every later block stops matching.
On AERE Network (chain id 2800), a new header is produced roughly every 500 ms under QBFT consensus by nine validators with a quorum of six. The consensus signatures that finalize each block are classical ECDSA secp256k1 today.
On chain 2800, the header is also where the post-quantum anchor lives. Since block 13,014,000, every 32nd header carries a certificate of Falcon-512 signatures from the validators over the parent block, and a 32-byte digest of that certificate sits inside the data covered by the block hash. At least 3 signatures are required per anchor block; in practice certificates carry 5, the configured cap. The keys that may sign are the 9 entries of the on-chain signer registry, which anyone can read.
Every header is checked twice: the producing client and a second, independently implemented client validate the chain side by side, which is what client diversity means in practice.
Verify it yourself
Verify it yourself: POST to https://rpc.aere.network the body {"jsonrpc":"2.0","id":1,"method":"eth_getBlockByNumber","params":["latest",false]} and inspect the returned header fields, including parentHash, stateRoot, timestamp, and extraData.