Bitcoin Forum

Bitcoin => Development & Technical Discussion => Topic started by: mustyoshi on March 08, 2014, 01:51:47 AM



Title: How would a node detect a reorganization/orphan of the blockchain?
Post by: mustyoshi on March 08, 2014, 01:51:47 AM
Such as it was downloading the wrong chain, and suddenly the chain ends?

Like if 2-3 blocks back was suddenly marked as orphaned, how would the qt client understand this had happened?


Title: Re: How would a node detect a reorganization/orphan of the blockchain?
Post by: oakpacific on March 08, 2014, 11:32:41 AM
A full node should be able to see every blockchain, sans the possibility of some MITM attacks.


Title: Re: How would a node detect a reorganization/orphan of the blockchain?
Post by: mustyoshi on March 08, 2014, 11:54:08 AM
A full node should be able to see every blockchain, sans the possibility of some MITM attacks.

What if the node is more like a 9/10ths node?


Title: Re: How would a node detect a reorganization/orphan of the blockchain?
Post by: oakpacific on March 08, 2014, 12:31:17 PM
A full node should be able to see every blockchain, sans the possibility of some MITM attacks.

What if the node is more like a 9/10ths node?

If you don't download the full copy of the blockchain you're not considered a full node. In that case(you download just the block headers) you're susceptible to sybil attack by some entities controlling more than 50% of the hashpower feeding you the wrong chain.


Title: Re: How would a node detect a reorganization/orphan of the blockchain?
Post by: mustyoshi on March 08, 2014, 08:52:58 PM
A full node should be able to see every blockchain, sans the possibility of some MITM attacks.

What if the node is more like a 9/10ths node?

If you don't download the full copy of the blockchain you're not considered a full node. In that case(you download just the block headers) you're susceptible to sybil attack by some entities controlling more than 50% of the hashpower feeding you the wrong chain.
Is there any way to defend against a sybil attack if I don't download every transaction, I do have some transactions, but not all of them?

How does a full node defend against an attacker with >50% of the hashpower?