Check Block Canonicality

Compare a block hash with the canonical hash at the same block number.

Use chain canonical to check whether a block hash matches the canonical block at its block number.

Command

rex chain canonical \
  --hash 0xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

Example Output

Canonical:

CHAIN CANONICAL

Requested hash: 0xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Found:          yes
Block number:   128
Canonical hash: 0xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Status:         canonical

Not canonical:

CHAIN CANONICAL

Requested hash: 0xbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
Found:          yes
Block number:   128
Canonical hash: 0xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Status:         not canonical

How It Works

The command:

• fetches the requested hash with eth_getBlockByHash
• reads that block’s number
• fetches the canonical block at that number with eth_getBlockByNumber
• compares the two hashes

If the requested hash cannot be fetched by the node, the status is unknown.