// Verify checks whether the block's nonce is valid.
func (l *Light) Verify(block pow.Block) bool {
// TODO: do ethash_quick_verify before getCache in order
// to prevent DOS attacks.
blockNum := block.NumberU64()
if blockNum >= epochLength*2048 {
glog.V(logger.Debug).Infof("block number %d too high, limit is %d", epochLength*2048)
return false
}
difficulty := block.Difficulty()
/* Cannot happen if block header diff is validated prior to PoW, but can
happen if PoW is checked first due to parallel PoW checking.
We could check the minimum valid difficulty but for SoC we avoid (duplicating)
Ethereum protocol consensus rules here which are not in scope of Ethash
*/
if difficulty.Cmp(common.Big0) == 0 {
glog.V(logger.Debug).Infof("invalid block difficulty")
return false
}
cache := l.getCache(blockNum)
dagSize := C.ethash_get_datasize(C.uint64_t(blockNum))
if l.test {
dagSize = dagSizeForTesting
}
// Recompute the hash using the cache.
hash := hashToH256(block.HashNoNonce())
ret := C.ethash_light_compute_internal(cache.ptr, dagSize, hash, C.uint64_t(block.Nonce()))
if !ret.success {
return false
}
// avoid mixdigest malleability as it's not included in a block's "hashNononce"
if block.MixDigest() != h256ToHash(ret.mix_hash) {
return false
}
// Make sure cache is live until after the C call.
// This is important because a GC might happen and execute
// the finalizer before the call completes.
_ = cache
// The actual check.
target := new(big.Int).Div(maxUint256, difficulty)
return h256ToHash(ret.result).Big().Cmp(target) <= 0
}
func Verify(block pow.Block) bool {
return verify(block.HashNoNonce(), block.Difficulty(), block.Nonce())
}