Data Structures

Internal data structures of blockchain objects and network messages.

Blockchain Objects

Signed transaction

Version 1 and 2

Field Name	Type	Length
Transaction type	Byte	1
Version	Byte	1
Transaction specific bytes
Proofs version	Byte (constant, value=1)	1
Proof size (N)	Short	2
Proof	Array[Byte]	N

Version 3+

Field Name	Type	Length
Transaction type	Byte	1
Version	Byte	1
Timestamp	Long	8
Sender's key type	KeyType (Byte)	1
Sender's public key	PublicKey (Array[Byte])	32 | 33
Fee	Long	8
Transaction specific bytes
Sponsor's key type	KeyType (Byte)	1
Sponsor's public key	PublicKey (Array[Byte])	0 | 32 | 33
Proofs version	Byte (constant, value=1)	1
Proof size (N)	Short	2
Proof	Array[Byte]	N

In version 3+ more fields are standardized. These are part of the transaction-specific bytes in versions 1 and 2.

Block

Field Name	Type	Length
Version (0x02 for Genesis block, 0x03 for common block)	Byte	0
Timestamp	Long	1
Parent block signature	Bytes	64
Consensus block length (always 40 bytes)	Int	4
Base target	Long	8
Generation signature*	Bytes	32
Transactions block length (N)	Int	8
Transaction #1 bytes	Bytes	M1
...	...	...
Transaction #K bytes	Bytes	MK
Generator's public key	Bytes	32
Block's signature	Bytes	64

Generation signature is calculated as blake2b256 hash of the following bytes:

Field Name	Type	Length
Previous block's generation signature	Bytes	32
Generator's public key	Bytes	32

Block's signature is calculated from the following bytes:

Field Name	Type	Length
Version (0x02 for Genesis block, 0x03 for common block)	Byte	0
Timestamp	Long	1
Parent block signature	Bytes	64
Consensus block length (always 40 bytes)	Int	4
Base target	Long	8
Generation signature*	Bytes	32
Transactions block length (N)	Int	8
Transaction #1 bytes	Bytes	M1
...	...	...
Transaction #K bytes	Bytes	MK
Generator's public key	Bytes	32

Network messages

Network message structure

All network messages share the same structure, except the Handshake.

Field name	Type	Length
Packet length (BigEndian)	Int	4
Magic Bytes	Bytes	4
Content ID	Byte	1
Payload length	Int	4
Payload checksum	Bytes	4
Payload	Bytes	N

Magic Bytes are 0x12 0x34 0x56 0x78. Payload checksum is the first 4 bytes of FastHash of Payload bytes. FastHash is the hash function Blake2b256(data).

Handshake message

Handshake is used to start communication between two nodes.

Field name	Type	Length
Application name length (N)	Byte	1
Application name (UTF-8 encoded bytes)	Bytes	N
Application version major	Int	4
Application version minor	Int	4
Application version patch	Int	4
Node name length (M)	Byte	1
Node name (UTF-8 encoded bytes)	Bytes	M
Node nonce	Long	8
Declared address length (K) or 0 if no declared address was set	Int	4
Declared address bytes (if length is not 0)	Bytes	K
Timestamp	Long	8

GetPeers message

GetPeers message is sent when sending node wants to know of other nodes on network.

Field name	Type	Length
Packet length (BigEndian)	Int	4
Magic Bytes	Bytes	4
Content ID (0x01)	Byte	1
Payload length	Int	4
Payload checksum	Bytes	4

Peers message

Peers message is a reply on GetPeers message.

Field name	Type	Length
Packet length (BigEndian)	Int	4
Magic Bytes	Bytes	4
Content ID (0x02)	Byte	1
Payload length	Int	4
Payload checksum	Bytes	4
Peers count (N)	Int	4
Peer #1 IP address	Bytes	4
Peer #1 port	Int	4
...	...	...
Peer #N IP address	Bytes	4
Peer #N port	Int	4

GetSignatures message

Field name	Type	Length
Packet length (BigEndian)	Int	4
Magic Bytes	Bytes	4
Content ID (0x14)	Byte	1
Payload length	Int	4
Payload checksum	Bytes	4
Block IDs count (N)	Int	4
Block #1 ID	Bytes	64
...	...	...
Block #N ID	Bytes	64

Signatures message

Field name	Type	Length
Packet length (BigEndian)	Int	4
Magic Bytes	Bytes	4
Content ID (0x15)	Byte	1
Payload length	Int	4
Payload checksum	Bytes	4
Block signatures count (N)	Int	4
Block #1 signature	Bytes	64
...	...	...
Block #N signature	Bytes	64

GetBlock message

Field name	Type	Length
Packet length (BigEndian)	Int	4
Magic Bytes	Bytes	4
Content ID (0x16)	Byte	1
Payload length	Int	4
Payload checksum	Bytes	4
Block ID	Bytes	64

Block message

Field name	Type	Length
Packet length (BigEndian)	Int	4
Magic Bytes	Bytes	4
Content ID (0x17)	Byte	1
Payload length	Int	4
Payload checksum	Bytes	4
Block bytes (N)	Bytes	N

Score message

Field name	Type	Length
Packet length (BigEndian)	Int	4
Magic Bytes	Bytes	4
Content ID (0x18)	Byte	1
Payload length	Int	4
Payload checksum	Bytes	4
Score (N bytes)	BigInt	N

Transaction message

Field name	Type	Length
Packet length (BigEndian)	Int	4
Magic Bytes	Bytes	4
Content ID (0x19)	Byte	1
Payload length	Int	4
Payload checksum	Bytes	4
Transaction (N bytes)	Bytes	N

Checkpoint message

Field name	Type	Length
Packet length (BigEndian)	Int	4
Magic Bytes	Bytes	4
Content ID (0x64)	Byte	1
Payload length	Int	4
Payload checksum	Bytes	4
Checkpoint items count (N)	Int	4
Checkpoint #1 height	Long	8
Checkpoint #1 signature	Bytes	64
...	...	...
Checkpoint #N height	Long	8
Checkpoint #N signature	Bytes	64