How to decode logsBloom

Question

Here is one block of my private blockchain

> eth.getBlock(63)
{
  difficulty: 134290,
  extraData: "0xd783010506846765746887676f312e372e33856c696e7578",
  gasLimit: 4038569465,
  gasUsed: 23114,
  hash: "0xa5d727b111f123e11b6dc5d271697b82a6238f83ab342088e0a1538afce7862d",
  logsBloom: "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008000000000000000000004000000000000200000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000",
  miner: "0x4c558858289c4180d0d2b994a4e009e078731191",
  mixHash: "0xba14e2b605aeacfa68f8345a9e30dd2d37dc4f3f4eba9e8ac8e744ded90ae566",
  nonce: "0x38de415ea086671a",
  number: 63,
  parentHash: "0xa7186a94afe92f0c0fedd1b8aa96e9aa92321e63a0b79d3f68ffe888bfb0239a",
  receiptsRoot: "0x303d0444bf28744722fd53a46144ead61f3515a82b9640603028ebf91f212126",
  sha3Uncles: "0x3633e886ef643c067d6fb7bfc1d2a6bf3eba939bf3cbb522f3894779ac1dd090",
  size: 1709,
  stateRoot: "0xcd4abaafec19113743df0235f06482f3a0b49e546e708055aa7a2382b232601e",
  timestamp: 1484750319,
  totalDifficulty: 8362288,
  transactions: ["0x1bd5825eac201f0f0e1e2c4a9ed5de026edc3f7fb02c4b912ca55c0f50a021fc"],
  transactionsRoot: "0xbaf6819c91ed625a97e974bbc4efd5808970b3b4991b1e2aca0dd537750aafc7",
  uncles: ["0x6f0a9ab0e468112fdcbbecd81ebebf929ca9a38e6a4c864e8164309d3bed42c6", "0xb4dd60c91ab18de3f72ba27ab5934bec66ab01798d18b599d1d298bd29e56204"]
}

How to decode the logsBloom?

Related, if not duplicate: http://ethereum.stackexchange.com/questions/3418/how-does-ethereum-make-use-of-bloom-filters — eth, Jan 20 '17 at 01:11
The referenced question doesn't really fully explain how to decide the bloom filter. It explains what the bloom filter is, but not how to decode it. — Thomas Jay Rush, Jan 23 '17 at 04:30

score 8 · Answer 1 · answered Aug 25 '18 at 16:31

8

There's not really anything to "decode".

A block or transaction bloom filter is a 2048 bit string. Every log that is emitted in a transaction has 0-4 topics. Each topic will set 3 bits to '1' based on the hash of the topic. Later, if you want to know whether a block or transaction has a given topic in one of its logs, you can check to see if those same 3 bits are set. If they aren't set, you know the topic won't be found in any transaction logs. If they are set, you can guess that they probably will be, but you still need to look at the transaction logs to be sure, because bloom filters have a risk of false positives.

answered Aug 25 '18 at 16:31

AusIV

621
5
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1

This is right, other than to say that the bloom includes some addresses in addition to the log topics. – Thomas Jay Rush Oct 28 '18 at 14:48
That's true, but the addresses are essentially treated as another topic, so you still can't really pull out the data that was put into the bloom filter, you can just test for its presence in the bloom filter. – AusIV Nov 01 '18 at 15:21
Yes. You’re exactly right. – Thomas Jay Rush Nov 01 '18 at 15:37

score 0 · Answer 2 · answered Apr 27 '18 at 03:45

in order to calculate HashNoNonce() value of the pending block logsbloom required without this it is impossible for a miner to verify if the hash he is mining on is corresponding to the particular block(proof of honest during mining). currently, it is not provided by RPC call.

How to decode logsBloom

2 Answers2