Lukas Fürderer
c4942dd716
This counters a possible attack where a miner could try to replace an already mined block with a different one that appears to be mined just one second before.
3.2 KiB
The carrotcoin protocol
There are two ways of communication:
- Node to Node
- Client to Node
General
Node to Node communication happens over IPv6 only.
When starting a node process, it tries to claim udp port 62039. If this port is not free, any other port is chosen.
Node behaviour
Peers
A node keeps a list of "peers". (IPv6 address + port number)
Each peer has a lifetime counter.
A node may drop a peer at any time by ignoring it.
A node may add new peers passively, when it gets contacted from a previously unknown address.
Within one minute, a node contacts all its peers and decrements the lifetime counter by one.
- When the counter reaches -1, the node is dropped from the peer list.
- Otherwise, a "heartbeat" message is sent to the peer.
When a node receives a "heartbeat" message from a peer, this peers lifetime counter is reset to 10.
At the beginning of each minute, the node creates a random "pairing" of all known peers with a lifetime counter >= 8.
The "heartbeat" message of a "paired" node includes the address and port number of the partner.
When a node receives a "heartbeat" message with an included partner, it adds this partner address to its peer list with a lifetime counter of 3.
Transactions
Each node keeps a list of up to 1024 open transactions. (That are valid but not yet part of the blockchain.)
The list is sorted by the following criteria:
- transaction fee, decreasing
- sender pubkey, increasing
- id, increasing
These sorting criteria form a 3-tuple.
Only one transaction per (sender pubkey, id) tuple stays in the list. If a transaction with the same tuple but greater transaction fee is received, it replaces the current transaction. If the transaction fee is equal or smaller, the new transaction is ignored.
If one sender created multiple transactions, it must have a large enough balance for all transactions, otherwise the excess ones (as defined by the sorting criteria above) are removed from the list.
If the list grows above 1024 entries, a node may either remove excess ones or keep them in a local list. Within the Node to Node communication, only the first 1024 entries will be synced.
Open transactions are hashed in a chain.
The hash of each open transaction is a SHA256, calculated over the following datastructure:
| content | length |
|---|---|
| previous hash | 32 |
| transaction fee (BE) | 8 |
| sender pubkey | 32 |
| id | 4 |
The "previous hash" consists of 32 nullbytes for the first transaction in the list. For all other entries, it is the calculated hash value of the open transaction entry directly before in the list.
If the list contains less than 1024 entries, set "transaction fee", "sender pubkey" and "id" to nullbytes for the hash calculation of all following entries.
Node to Node message packet formats
heartbeat message
| content | size (bytes) |
|---|---|
| protocol version = 0 (BE) | 2 |
| capable version = 0 (BE) | 2 |
| type = 0 (BE) | 1 |
| difficulty sum of second last known block (BE) | 32 |
| hash value of open transaction # 1023 | 32 |
| partner IPv6 | 16 |
| partner port (BE) | 2 |
The difficulty sum is sent as 2^28 if only one block is known or as 0 if no block is known.
partner IPv6 and partner port may be nullbytes (no partner included).