// Pseudocode: PVM-side validation sketch
verify(tx):
  msg = keccak256(encodeTxForSig(tx))
  pub = ecrecover(msg, tx.v, tx.r, tx.s)
  require(address(pub) == tx.from)
  require(tx.nonce == account.nonce)
  // gas accounting & state updates proceed

// Conceptual block processing
for (tx of block.txs):
  result = PVM.execute(tx, state)
commit:
  stateRoot    = MPT(state)
  receiptsRoot = MPT(receipts)
  header.stateRoot = stateRoot
  header.receiptsRoot = receiptsRoot

// Block header sketch
header = {
  parentHash,
  stateRoot,
  txRoot,
  time,
  nonce,
  difficulty,
  mixHash,      // XHash result
}
assert(block.parent.hash == parentHash)
assert(XHash(header) < target(difficulty))

// Choose chain with max cumulative work
best = argmax(chains, sum(block.work for block in chain))