# Protocol Documentation
## Table of Contents
- [Protocol Documentation](#protocol-documentation)
- [Table of Contents](#table-of-contents)
- [refs/types.proto](#refstypesproto)
- [Message Address](#message-address)
- [Message Checksum](#message-checksum)
- [Message ContainerID](#message-containerid)
- [Message ObjectID](#message-objectid)
- [Message OwnerID](#message-ownerid)
- [Message Signature](#message-signature)
- [Message SignatureRFC6979](#message-signaturerfc6979)
- [Message Version](#message-version)
- [ChecksumType](#checksumtype)
- [SignatureScheme](#signaturescheme)
- [Scalar Value Types](#scalar-value-types)
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## refs/types.proto
### Message Address
Objects in NeoFS are addressed by their ContainerID and ObjectID.
String presentation of `Address` is a concatenation of string encoded
`ContainerID` and `ObjectID` delimited by '/' character.
| Field | Type | Label | Description |
| ----- | ---- | ----- | ----------- |
| container_id | [ContainerID](#neo.fs.v2.refs.ContainerID) | | Container identifier |
| object_id | [ObjectID](#neo.fs.v2.refs.ObjectID) | | Object identifier |
### Message Checksum
Checksum message.
Depending on checksum algorithm type, the string presentation may vary:
* TZ \
Hex encoded string without `0x` prefix
* SHA256 \
Hex encoded string without `0x` prefix
| Field | Type | Label | Description |
| ----- | ---- | ----- | ----------- |
| type | [ChecksumType](#neo.fs.v2.refs.ChecksumType) | | Checksum algorithm type |
| sum | [bytes](#bytes) | | Checksum itself |
### Message ContainerID
NeoFS container identifier. Container structures are immutable and
content-addressed.
`ContainerID` is a 32 byte long
[SHA256](https://csrc.nist.gov/publications/detail/fips/180/4/final) hash of
stable-marshalled container message.
String presentation is a
[base58](https://tools.ietf.org/html/draft-msporny-base58-02) encoded string.
JSON value will be data encoded as a string using standard base64
encoding with paddings. Either
[standard](https://tools.ietf.org/html/rfc4648#section-4) or
[URL-safe](https://tools.ietf.org/html/rfc4648#section-5) base64 encoding
with/without paddings are accepted.
| Field | Type | Label | Description |
| ----- | ---- | ----- | ----------- |
| value | [bytes](#bytes) | | Container identifier in a binary format. |
### Message ObjectID
NeoFS Object unique identifier. Objects are immutable and content-addressed.
It means `ObjectID` will change if the `header` or the `payload` changes.
`ObjectID` is a 32 byte long
[SHA256](https://csrc.nist.gov/publications/detail/fips/180/4/final) hash of
the object's `header` field, which, in it's turn, contains the hash of the object's
payload.
String presentation is a
[base58](https://tools.ietf.org/html/draft-msporny-base58-02) encoded string.
JSON value will be data encoded as a string using standard base64
encoding with paddings. Either
[standard](https://tools.ietf.org/html/rfc4648#section-4) or
[URL-safe](https://tools.ietf.org/html/rfc4648#section-5) base64 encoding
with/without paddings are accepted.
| Field | Type | Label | Description |
| ----- | ---- | ----- | ----------- |
| value | [bytes](#bytes) | | Object identifier in a binary format |
### Message OwnerID
`OwnerID` is a derivative of a user's main public key. The transformation
algorithm is the same as for Neo3 wallet addresses. Neo3 wallet address can
be directly used as `OwnerID`.
`OwnerID` is a 25 bytes sequence starting with Neo version prefix byte
followed by 20 bytes of ScrptHash and 4 bytes of checksum.
String presentation is a [Base58
Check](https://en.bitcoin.it/wiki/Base58Check_encoding) Encoded string.
JSON value will be data encoded as a string using standard base64
encoding with paddings. Either
[standard](https://tools.ietf.org/html/rfc4648#section-4) or
[URL-safe](https://tools.ietf.org/html/rfc4648#section-5) base64 encoding
with/without paddings are accepted.
| Field | Type | Label | Description |
| ----- | ---- | ----- | ----------- |
| value | [bytes](#bytes) | | Identifier of the container owner in a binary format |
### Message Signature
Signature of something in NeoFS.
| Field | Type | Label | Description |
| ----- | ---- | ----- | ----------- |
| key | [bytes](#bytes) | | Public key used for signing |
| sign | [bytes](#bytes) | | Signature |
| scheme | [SignatureScheme](#neo.fs.v2.refs.SignatureScheme) | | Scheme contains digital signature scheme identifier |
### Message SignatureRFC6979
RFC 6979 signature.
| Field | Type | Label | Description |
| ----- | ---- | ----- | ----------- |
| key | [bytes](#bytes) | | Public key used for signing |
| sign | [bytes](#bytes) | | Deterministic ECDSA with SHA-256 hashing |
### Message Version
API version used by a node.
String presentation is a Semantic Versioning 2.0.0 compatible version string
with 'v' prefix. i.e. `vX.Y`, where `X` is the major number, `Y` is the minor number.
| Field | Type | Label | Description |
| ----- | ---- | ----- | ----------- |
| major | [uint32](#uint32) | | Major API version |
| minor | [uint32](#uint32) | | Minor API version |
### ChecksumType
Checksum algorithm type.
| Name | Number | Description |
| ---- | ------ | ----------- |
| CHECKSUM_TYPE_UNSPECIFIED | 0 | Unknown. Not used |
| TZ | 1 | Tillich-Zemor homomorphic hash function |
| SHA256 | 2 | SHA-256 |
### SignatureScheme
Signature scheme describes digital signing scheme used for (key, signature) pair.
| Name | Number | Description |
| ---- | ------ | ----------- |
| ECDSA_SHA512 | 0 | ECDSA with SHA-512 hashing (FIPS 186-3) |
| ECDSA_RFC6979_SHA256 | 1 | Deterministic ECDSA with SHA-256 hashing (RFC 6979) |
| ECDSA_RFC6979_SHA256_WALLET_CONNECT | 2 | Deterministic ECDSA with SHA-256 hashing using WalletConnect API. Here the algorithm is the same, but the message format differs. |
## Scalar Value Types
| .proto Type | Notes | C++ Type | Java Type | Python Type |
| ----------- | ----- | -------- | --------- | ----------- |
| double | | double | double | float |
| float | | float | float | float |
| int32 | Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint32 instead. | int32 | int | int |
| int64 | Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint64 instead. | int64 | long | int/long |
| uint32 | Uses variable-length encoding. | uint32 | int | int/long |
| uint64 | Uses variable-length encoding. | uint64 | long | int/long |
| sint32 | Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int32s. | int32 | int | int |
| sint64 | Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int64s. | int64 | long | int/long |
| fixed32 | Always four bytes. More efficient than uint32 if values are often greater than 2^28. | uint32 | int | int |
| fixed64 | Always eight bytes. More efficient than uint64 if values are often greater than 2^56. | uint64 | long | int/long |
| sfixed32 | Always four bytes. | int32 | int | int |
| sfixed64 | Always eight bytes. | int64 | long | int/long |
| bool | | bool | boolean | boolean |
| string | A string must always contain UTF-8 encoded or 7-bit ASCII text. | string | String | str/unicode |
| bytes | May contain any arbitrary sequence of bytes. | string | ByteString | str |