P2P message format¶

This page details the structure and layout of messages used by the Tezos P2P layer.

The elementary types used for message or header fields are documented in the Data_encoding module, for example:

Additionally, the type unsigned 30-bit integer is used to denote the subset of positive integers of type signed 31-bit integers.

Note

31-bit integers: The internal representation of integers in OCaml reserves one bit for GC tagging. The remaining bits encode a signed integer. For compatibility with 32-bit machines, we restrict these native integers to the 31-bit range.

Block header (shell)¶

Name	Size	Contents
level	4 bytes	signed 32-bit integer
proto	1 byte	unsigned 8-bit integer
predecessor	32 bytes	bytes
timestamp	8 bytes	signed 64-bit integer
validation_pass	1 byte	unsigned 8-bit integer
operations_hash	32 bytes	bytes
# bytes in field “fitness”	4 bytes	unsigned 30-bit integer
fitness	Variable	sequence of $fitness.elem
context	32 bytes	bytes
protocol_data	Variable	bytes

fitness.elem¶

Name	Size	Contents
# bytes in next field	4 bytes	unsigned 30-bit integer
Unnamed field 0	Variable	bytes

Operation (shell)¶

Name	Size	Contents
branch	32 bytes	bytes
data	Variable	bytes

Block_header (alpha-specific)¶

Name	Size	Contents
payload_hash	32 bytes	bytes
payload_round	4 bytes	signed 32-bit integer
proof_of_work_nonce	8 bytes	bytes
? presence of field “seed_nonce_hash”	1 byte	boolean (0 for false, 255 for true)
seed_nonce_hash	32 bytes	bytes
liquidity_baking_escape_vote	1 byte	boolean (0 for false, 255 for true)
signature	64 bytes	bytes

Operation (alpha-specific)¶

Name	Size	Contents
contents	Variable	sequence of $alpha.operation.alpha.contents
signature	64 bytes	bytes

alpha.scripted.contracts¶

Name	Size	Contents
# bytes in next field	4 bytes	unsigned 30-bit integer
code	Variable	bytes
# bytes in next field	4 bytes	unsigned 30-bit integer
storage	Variable	bytes

alpha.contract_id (22 bytes, 8-bit tag)¶

Implicit (tag 0)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
Signature.Public_key_hash	21 bytes	$public_key_hash

Originated (tag 1)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
Contract_hash	20 bytes	bytes
padding	1 byte	padding

alpha.entrypoint (Determined from data, 8-bit tag)¶

default (tag 0)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer

root (tag 1)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer

do (tag 2)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer

set_delegate (tag 3)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer

remove_delegate (tag 4)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer

named (tag 255)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
# bytes in next field	1 byte	unsigned 8-bit integer
Unnamed field 0	Variable	bytes

X_0¶

Name	Size	Contents
entrypoint	Determined from data	$alpha.entrypoint
# bytes in next field	4 bytes	unsigned 30-bit integer
value	Variable	bytes

N.t¶

A variable-length sequence of bytes encoding a Zarith natural number. Each byte has a running unary size bit: the most significant bit of each byte indicates whether this is the last byte in the sequence (0) or whether the sequence continues (1). Size bits ignored, the data is the binary representation of the number in little-endian order.

Name	Size	Contents
N.t	Determined from data	bytes

public_key (Determined from data, 8-bit tag)¶

Ed25519 (tag 0)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
Ed25519.Public_key	32 bytes	bytes

Secp256k1 (tag 1)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
Secp256k1.Public_key	33 bytes	bytes

P256 (tag 2)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
P256.Public_key	33 bytes	bytes

alpha.inlined.preendorsement.contents (43 bytes, 8-bit tag)¶

Preendorsement (tag 20)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
slot	2 bytes	unsigned 16-bit integer
level	4 bytes	signed 32-bit integer
round	4 bytes	signed 32-bit integer
block_payload_hash	32 bytes	bytes

alpha.inlined.preendorsement¶

Name	Size	Contents
branch	32 bytes	bytes
operations	43 bytes	$alpha.inlined.preendorsement.contents
signature	Variable	bytes

public_key_hash (21 bytes, 8-bit tag)¶

Ed25519 (tag 0)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
Ed25519.Public_key_hash	20 bytes	bytes

Secp256k1 (tag 1)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
Secp256k1.Public_key_hash	20 bytes	bytes

P256 (tag 2)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
P256.Public_key_hash	20 bytes	bytes

fitness.elem¶

Name	Size	Contents
# bytes in next field	4 bytes	unsigned 30-bit integer
Unnamed field 0	Variable	bytes

alpha.block_header.alpha.full_header¶

Name	Size	Contents
level	4 bytes	signed 32-bit integer
proto	1 byte	unsigned 8-bit integer
predecessor	32 bytes	bytes
timestamp	8 bytes	signed 64-bit integer
validation_pass	1 byte	unsigned 8-bit integer
operations_hash	32 bytes	bytes
# bytes in field “fitness”	4 bytes	unsigned 30-bit integer
fitness	Variable	sequence of $fitness.elem
context	32 bytes	bytes
payload_hash	32 bytes	bytes
payload_round	4 bytes	signed 32-bit integer
proof_of_work_nonce	8 bytes	bytes
? presence of field “seed_nonce_hash”	1 byte	boolean (0 for false, 255 for true)
seed_nonce_hash	32 bytes	bytes
liquidity_baking_escape_vote	1 byte	boolean (0 for false, 255 for true)
signature	64 bytes	bytes

alpha.inlined.endorsement_mempool.contents (43 bytes, 8-bit tag)¶

Endorsement (tag 21)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
slot	2 bytes	unsigned 16-bit integer
level	4 bytes	signed 32-bit integer
round	4 bytes	signed 32-bit integer
block_payload_hash	32 bytes	bytes

alpha.inlined.endorsement¶

Name	Size	Contents
branch	32 bytes	bytes
operations	43 bytes	$alpha.inlined.endorsement_mempool.contents
signature	Variable	bytes

alpha.operation.alpha.contents (Determined from data, 8-bit tag)¶

Seed_nonce_revelation (tag 1)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
level	4 bytes	signed 32-bit integer
nonce	32 bytes	bytes

Double_endorsement_evidence (tag 2)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
# bytes in next field	4 bytes	unsigned 30-bit integer
op1	Variable	$alpha.inlined.endorsement
# bytes in next field	4 bytes	unsigned 30-bit integer
op2	Variable	$alpha.inlined.endorsement

Double_baking_evidence (tag 3)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
# bytes in next field	4 bytes	unsigned 30-bit integer
bh1	Determined from data	$alpha.block_header.alpha.full_header
# bytes in next field	4 bytes	unsigned 30-bit integer
bh2	Determined from data	$alpha.block_header.alpha.full_header

Activate_account (tag 4)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
pkh	20 bytes	bytes
secret	20 bytes	bytes

Proposals (tag 5)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
source	21 bytes	$public_key_hash
period	4 bytes	signed 32-bit integer
# bytes in next field	4 bytes	unsigned 30-bit integer
proposals	Variable	sequence of bytes

Ballot (tag 6)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
source	21 bytes	$public_key_hash
period	4 bytes	signed 32-bit integer
proposal	32 bytes	bytes
ballot	1 byte	signed 8-bit integer

Double_preendorsement_evidence (tag 7)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
# bytes in next field	4 bytes	unsigned 30-bit integer
op1	Variable	$alpha.inlined.preendorsement
# bytes in next field	4 bytes	unsigned 30-bit integer
op2	Variable	$alpha.inlined.preendorsement

Failing_noop (tag 17)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
# bytes in next field	4 bytes	unsigned 30-bit integer
arbitrary	Variable	bytes

Preendorsement (tag 20)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
slot	2 bytes	unsigned 16-bit integer
level	4 bytes	signed 32-bit integer
round	4 bytes	signed 32-bit integer
block_payload_hash	32 bytes	bytes

Endorsement (tag 21)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
slot	2 bytes	unsigned 16-bit integer
level	4 bytes	signed 32-bit integer
round	4 bytes	signed 32-bit integer
block_payload_hash	32 bytes	bytes

Reveal (tag 107)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
source	21 bytes	$public_key_hash
fee	Determined from data	$N.t
counter	Determined from data	$N.t
gas_limit	Determined from data	$N.t
storage_limit	Determined from data	$N.t
public_key	Determined from data	$public_key

Transaction (tag 108)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
source	21 bytes	$public_key_hash
fee	Determined from data	$N.t
counter	Determined from data	$N.t
gas_limit	Determined from data	$N.t
storage_limit	Determined from data	$N.t
amount	Determined from data	$N.t
destination	22 bytes	$alpha.contract_id
? presence of field “parameters”	1 byte	boolean (0 for false, 255 for true)
parameters	Determined from data	$X_0

Origination (tag 109)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
source	21 bytes	$public_key_hash
fee	Determined from data	$N.t
counter	Determined from data	$N.t
gas_limit	Determined from data	$N.t
storage_limit	Determined from data	$N.t
balance	Determined from data	$N.t
? presence of field “delegate”	1 byte	boolean (0 for false, 255 for true)
delegate	21 bytes	$public_key_hash
script	Determined from data	$alpha.scripted.contracts

Delegation (tag 110)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
source	21 bytes	$public_key_hash
fee	Determined from data	$N.t
counter	Determined from data	$N.t
gas_limit	Determined from data	$N.t
storage_limit	Determined from data	$N.t
? presence of field “delegate”	1 byte	boolean (0 for false, 255 for true)
delegate	21 bytes	$public_key_hash

Register_global_constant (tag 111)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
source	21 bytes	$public_key_hash
fee	Determined from data	$N.t
counter	Determined from data	$N.t
gas_limit	Determined from data	$N.t
storage_limit	Determined from data	$N.t
# bytes in next field	4 bytes	unsigned 30-bit integer
value	Variable	bytes

Set_deposits_limit (tag 112)¶

Name	Size	Contents
Tag	1 byte	unsigned 8-bit integer
source	21 bytes	$public_key_hash
fee	Determined from data	$N.t
counter	Determined from data	$N.t
gas_limit	Determined from data	$N.t
storage_limit	Determined from data	$N.t
? presence of field “limit”	1 byte	boolean (0 for false, 255 for true)
limit	Determined from data	$N.t