Function header_chain 

pub fn header_chain(
    builder: &CircuitBuilder,
    headers: &[[Wire; 10]],
) -> [Wire; 4]

Returns hash(headers[0]), the digest of the latest block in the chain.

Asserts the following things:

• previous_block_hash(headers[i]) = hash(headers[i+1]) (hash chain)
• hash(headers[i]) < target(headers[i]) (proof of work)

The digest of the head is returned rather than asserted, so the caller decides what to compare it against.

IMPORTANT: This does currently NOT assert that target(headers[i]) is in any way related to target(headers[i+1]), like it must be in the Bitcoin protocol. In particular, this means that one can easily satisfy this circuit with a self-mined sequence of blocks which have low difficulty.

Note: It also doesn’t check many other things about the block header, like that the constraints on the timestamps.

Panics

If headers is empty.