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CIP-0019: Cardano Addresses (#78)
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* outline first draft of CIP-0019 about Cardano addresses.

* complete section about stake addresses and review grammar.

* revise test vectors to include example for all types
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KtorZ committed May 4, 2021
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36 changes: 36 additions & 0 deletions CIP-0019/CIP-0019-byron-addresses.cddl
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BYRON_ADDRESS =
( #6.24(<<BYRON_ADDRESS_PAYLOAD>>)
, uint32 ; crc32 of the CBOR serialized address payload
)

BYRON_ADDRESS_PAYLOAD =
( bytes .size 28 ; blake2b_224(sha3_256(BYRON_ADDRESS_ROOT)) digest
, BYRON_ADDRESS_ATTRIBUTES
, BYRON_ADDRESS_TYPE
)

BYRON_ADDRESS_ROOT =
( BYRON_ADDRESS_TYPE
, BYRON_ADDRESS_SPENDING_DATA
, BYRON_ADDRESS_ATTRIBUTES
)

BYRON_ADDRESS_TYPE =
0 ; Public key
// 2 ; Redemption

BYRON_ADDRESS_SPENDING_DATA =
( 0, bytes .size 64 ) ; Ed25519 Public key | Associated BIP-32 chain code
//
( 2, bytes .size 32 ) ; Ed25519 Public key

BYRON_ADDRESS_ATTRIBUTES =
{ 1 : <<bytes .cbor BYRON_DERIVATION_PATH_CIPHERTEXT>> ; Double CBOR-encoded ChaCha20/Poly1305 encrypted digest, see CIP for details.
, 2 : <<uint32>> ; CBOR-encoded network discriminant
}

BYRON_DERIVATION_PATH_CIPHERTEXT = ; Obtained by encrypting a serialized derivation path
bytes .size 28

BYRON_DERIVATION_PATH =
[ * uint32 ]
28 changes: 28 additions & 0 deletions CIP-0019/CIP-0019-cardano-addresses.abnf
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ADDRESS = %b0000 | NETWORK-TAG | KEY-HASH | KEY-HASH ; type 00, Base Shelley address
\ %b0001 | NETWORK-TAG | SCRIPT-HASH | KEY-HASH ; type 01, Base Shelley address
\ %b0010 | NETWORK-TAG | KEY-HASH | SCRIPT-HASH ; type 02, Base Shelley address
\ %b0011 | NETWORK-TAG | SCRIPT-HASH | SCRIPT-HASH ; type 03, Base Shelley address
\ %b0100 | NETWORK-TAG | KEY-HASH | POINTER ; type 04, Pointer Shelley address
\ %b0101 | NETWORK-TAG | SCRIPT-HASH | POINTER ; type 05, Pointer Shelley address
\ %b0110 | NETWORK-TAG | KEY-HASH ; type 06, Payment Shelley address
\ %b0111 | NETWORK-TAG | SCRIPT-HASH ; type 07, Payment Shelley address
\ %b1110 | NETWORK-TAG | KEY-HASH ; type 08, Stake Shelley address
\ %b1111 | NETWORK-TAG | SCRIPT-HASH ; type 09, Stake Shelley address
\ %b1000 | BYRON-PAYLOAD ; type 10, Byron / Bootstrap address

NETWORK-TAG = %b0000 ; Testnet
\ %b0001 ; Mainnet

POINTER = VARIABLE-LENGTH-UINT ; slot number
| VARIABLE-LENGTH-UINT ; transaction index
| VARIABLE-LENGTH-UINT ; output index

VARIABLE-LENGTH-UINT = (%b1 | UINT7 | VARIABLE-LENGTH-UINT)
/ (%b0 | UINT7)
UINT7 = 7BIT

KEY-HASH = 28OCTET

SCRIPT-HASH= 28OCTET

BYRON-PAYLOAD = *OCTET ; see 'Byron Addresses' section or cddl specification.
236 changes: 236 additions & 0 deletions CIP-0019/CIP-0019.md
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---
CIP: 19
Title: Cardano Addresses
Authors: Matthias Benkort <matthias.benkort@iohk.io>
Comments-Summary: A description of the structure of addresses in Cardano.
Comments-URI: https://github.com/cardano-foundation/CIPs/wiki/Comments:CIP-0019
Status: Active
Type: Standards
Created: 2020-03-25
License: CC-BY-4.0
---

# Abstract

This specification describes the binary structure of addresses in Cardano, covering both addresses introduced in the Shelley era and the legacy format from the Byron era.

# Motivation

Document design choices for posterity. Most applications interacting with the Cardano blockchain will likely not have any need for this level of details, however, some might. This CIP is meant to capture this knowledge.

# Specification

## Overview

In Cardano, addresses are comprised of two parts, a **header** and a **payload**. Depending on the header, the interpretation of the payload varies.

In the header, bits [7;4] indicate the type of addresses being used; we'll call these four bits the **header type**. The remaining four bits [3;0] are either unused or refer to what we'll call the **network tag**. There are currently 11 types of addresses in Cardano which we'll divide into three categories: [Shelley addresses], [stake addresses], and [Byron addresses].

```
1 byte variable length
<------> <------------------->
┌────────┬─────────────────────┐
│ header │ payload │
└────────┴─────────────────────┘
🔎
╎ 7 6 5 4 3 2 1 0
╎ ┌─┬─┬─┬─┬─┬─┬─┬─┐
╰╌╌╌╌╌╌╌╌ │t│t│t│t│n│n│n│n│
└─┴─┴─┴─┴─┴─┴─┴─┘
```

See also the more detailed [ABNF grammar in annex].

#### Network Tag

Except for [Byron addresses] (type 8 = `1000`), the second half of the header (bits [3;0]) refers to the network tag which can have the following values and semantics. Other values of the network tag are currently reserved for future network types. In the case of [Byron addresses], bits [3;0] have a completely separate definition detailed in the section below.

Network Tag (`. . . . n n n n`) | Semantic
--- | ---
`....0000` | Testnet(s)
`....0001` | Mainnet

#### User-facing Encoding

By convention, Shelley and stake addresses are encoded using [bech32] with human-readable prefixes defined in [CIP-0005]. Byron addresses are however encoded in [base58]. Historically, Byron addresses were introduced before the design of bech32, which solves various issues of the base58 encoding format (see [bech32's motivation](https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki#motivation) for more detail). Byron addresses were however kept as Base58 to easily distinguish them from new addresses introduced in Shelley, massively making use of bech32 for encoding small binary objects.

Summarizing:

| Address Type | Encoding | Example |
| --- | --- | --- |
| Byron | Base58 | `37btjrVyb4KDXBNC4haBVPCrro8AQPHwvCMp3RFhhSVWwfFmZ6wwzSK6JK1hY6wHNmtrpTf1kdbva8TCneM2YsiXT7mrzT21EacHnPpz5YyUdj64na` |
| Shelley | bech32 | `addr1vpu5vlrf4xkxv2qpwngf6cjhtw542ayty80v8dyr49rf5eg0yu80w` |
| stake | bech32 | `stake1vpu5vlrf4xkxv2qpwngf6cjhtw542ayty80v8dyr49rf5egfu2p0u` |


## Shelley Addresses

There are currently 8 types of Shelley addresses summarized in the table below:

Header type (`t t t t . . . .`) | Payment Part | Delegation Part
--- | --- | ---
(0) `0000....` | `PaymentKeyHash` | `StakeKeyHash`
(1) `0001....` | `ScriptHash` | `StakeKeyHash`
(2) `0010....` | `PaymentKeyHash` | `ScriptHash`
(3) `0011....` | `ScriptHash` | `ScriptHash`
(4) `0100....` | `PaymentKeyHash` | `Pointer`
(5) `0101....` | `ScriptHash` | `Pointer`
(6) `0110....` | `PaymentKeyHash` | ø
(7) `0111....` | `ScriptHash` | ø

- `PubKeyHash` and `StakeKeyHash` refers to `blake2b-224` hash digests of Ed25519 verification keys. How keys are obtained is out of the scope of this specification. Interested readers may look at [CIP-1852] for more details.

- `ScriptHash` refer to `blake2b-224` hash digests of serialized monetary scripts. How scripts are constructed and serialized is out of the scope of this specification.

- `Pointer` is detailed in the section below.

#### Payment part

Fundamentally, the first part of a Shelley address indicates the ownership of the funds associated with the address. We call it, the **payment part**. Whoever owns the payment parts owns any funds at the address. As a matter of fact, in order to spend from an address, one must provide a witness attesting that the address can be spent. In the case of a `PubKeyHash`, it means providing a signature of the transaction body made with the signing key corresponding to the hashed public key (as well as the public key itself for verification). For monetary scripts, it means being able to provide the source script and meet the necessary conditions to validate the script.

#### Delegation part

The second part of a Shelley address indicates the owner of the stake rights associated with the address. We call it, the **delegation part**. Whoever owns the delegation parts owns the stake rights of any funds associated with the address. In most scenarios, the payment part and the delegation part are owned by the same party. Yet it is possible to construct addresses where both parts are owned and managed by separate entities. We call such addresses **mangled addresses** or **hybrid addresses**.

Some addresses (types 6 and 7) carry no delegation part whatsoever. Their associated stake can't be delegated. They can be used by parties who want to prove that they are not delegating funds which is typically the case for custodial businesses managing funds on the behalf of other stakeholders. Delegation parts can also be defined in terms of on-chain [pointers].

#### Pointers

In an address, a **chain pointer** refers to a point of the chain containing a stake key registration certificate. A point is identified by 3 coordinates:

- An absolute slot number
- A transaction index (within that slot)
- An output index (within that transaction)

These coordinates form a concise way of referring to a stake key (typically half the size of a stake key hash). They are serialized as three variable-length positive numbers following the ABNF grammar here below:

```abnf
POINTER = VARIABLE-LENGTH-UINT ; slot number
| VARIABLE-LENGTH-UINT ; transaction index
| VARIABLE-LENGTH-UINT ; output index
VARIABLE-LENGTH-UINT = (%b1 | UINT7 | VARIABLE-LENGTH-UINT)
/ (%b0 | UINT7)
UINT7 = 7BIT
```

## Stake Addresses

Like [Shelley addresses], stake addresses (also known as **reward addresses**) start with a single header byte identifying their type and the network, followed by 28 bytes of payload identifying either a stake key hash or a script hash.

Header type (`t t t t . . . .`) | Stake Reference
--- | ---
(8) `1110....` | `StakeKeyHash`
(9) `1111....` | `ScriptHash`

- `StakeKeyHash` refers to `blake2b-224` hash digests of Ed25519 verification keys. How keys are obtained is out of the scope of this specification. Interested readers may look at [CIP-1852] for more details.

- `ScriptHash` refers to `blake2b-224` hash digests of serialized monetary scripts. How scripts are constructed and serialized is out of the scope of this specification.

## Byron Addresses

Before diving, please acknowledge that a lot of the supported capabilities of Byron addresses have remained mainly unused. The initial design showed important trade-offs and rendered it unpractical to sustain the long-term goals of the network. A new format was created when introducing Shelley and Byron addresses were kept only for backward compatibility. Byron addresses are also sometimes called **bootstrap addresses**.


Like many other objects on the Cardano blockchain yet unlike Shelley addresses, Byron addresses are [CBOR]-encoded binary objects. Conveniently enough, the first 4 bits of their first byte are always equal to `1000....` which allows us to land back on our feet w.r.t to the address type. Their internal structure is however vastly different and a bit unusual.

```
┌────────┬──────────────┬────────┐
│ root │ attributes │ type │
└────────┴──────────────┴────────┘
╎ ╎ ╎
╎ ╎ ╰╌╌ Standard
╎ ╎ ╰╌╌ Redeem
╎ ╎
╎ ╰╌╌ Derivation Path
╎ ╰╌╌ Network Tag
╎
╎ ┌────────┬─────────────────┬──────────────┐
╰╌╌╌╌ double-hash ( │ type │ spending data │ attributes │ )
└────────┴─────────────────┴──────────────┘
╎
╰╌╌ Verification Key
╰╌╌ Redemption Key
```

The address `root` uniquely identifies the address and is a double-hash digest (SHA3-256, and then Blake2b-224) of the address type, spending data, and attributes.

Then comes the address attributes which are both optional. The network tag is present only on test networks and contains an identifier that is used for network discrimination. The [derivation path] (detailed below) was used by legacy so-called random wallets in the early days of Cardano and its usage was abandoned with the introduction of Yoroi and so-called **Icarus addresses**.

Finally, the address type allows for distinguishing different sub-types of Byron addresses. **Redeem addresses** are used inside the Byron genesis configuration and were given to early investors who helped to fund the project.

A full and more detailed [CDDL specification of Byron addresses] is given in the annex to the CIP.

#### Derivation path

Historically, Cardano wallets have been storing information about the wallet structure directly within the address. This information comes in the form of two derivation indexes (in the sense of child key derivation as defined in [BIP-0032]) which we call **derivation path**. To protect the wallet's anonymity, the derivation path is stored encrypted using a ChaCha20/Poly1305 authenticated cipher.

# Rationale

N/A

# Backwards Compatibility

N/A

# Reference Implementation(s)

- [input-output-hk/cardano-addresses (Byron & Shelley)](https://github.com/input-output-hk/cardano-addresses)

- [input-output-hk/cardano-ledger-specs (Byron)](https://github.com/input-output-hk/cardano-ledger-specs/blob/d5eaac6c4b21a8e69dc3a5503a72e3c3bfde648e/byron/ledger/impl/src/Cardano/Chain/Common/Address.hs)

- [input-output-hk/cardano-ledger-specs (Shelley)](https://github.com/input-output-hk/cardano-ledger-specs/blob/1e7e6e03a46e8118b318ed105214767aec0f3976/shelley/chain-and-ledger/executable-spec/src/Shelley/Spec/Ledger/Address.hs)

# Test Vectors

All test vectors below use the following payment key, stake key, script and pointer:

- `addr_vk1w0l2sr2zgfm26ztc6nl9xy8ghsk5sh6ldwemlpmp9xylzy4dtf7st80zhd`
- `stake_vk1px4j0r2fk7ux5p23shz8f3y5y2qam7s954rgf3lg5merqcj6aetsft99wu`
- `script1cda3khwqv60360rp5m7akt50m6ttapacs8rqhn5w342z7r35m37`
- `(2498243, 27, 3)`

```yaml
mainnet:
type-00: addr1qx2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzer3n0d3vllmyqwsx5wktcd8cc3sq835lu7drv2xwl2wywfgse35a3x
type-01: addr1z8phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gten0d3vllmyqwsx5wktcd8cc3sq835lu7drv2xwl2wywfgs9yc0hh
type-02: addr1yx2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzerkr0vd4msrxnuwnccdxlhdjar77j6lg0wypcc9uar5d2shs2z78ve
type-03: addr1x8phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gt7r0vd4msrxnuwnccdxlhdjar77j6lg0wypcc9uar5d2shskhj42g
type-04: addr1gx2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzer5pnz75xxcrzqf96k
type-05: addr128phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtupnz75xxcrtw79hu
type-06: addr1vx2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzers66hrl8
type-07: addr1w8phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtcyjy7wx
type-08: stake1uyehkck0lajq8gr28t9uxnuvgcqrc6070x3k9r8048z8y5gh6ffgw
type-09: stake178phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtcccycj5

testnet:
type-00: addr_test1qz2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzer3n0d3vllmyqwsx5wktcd8cc3sq835lu7drv2xwl2wywfgs68faae
type-01: addr_test1zrphkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gten0d3vllmyqwsx5wktcd8cc3sq835lu7drv2xwl2wywfgsxj90mg
type-02: addr_test1yz2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzerkr0vd4msrxnuwnccdxlhdjar77j6lg0wypcc9uar5d2shsf5r8qx
type-03: addr_test1xrphkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gt7r0vd4msrxnuwnccdxlhdjar77j6lg0wypcc9uar5d2shs4p04xh
type-04: addr_test1gz2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzer5pnz75xxcrdw5vky
type-05: addr_test12rphkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtupnz75xxcryqrvmw
type-06: addr_test1vz2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzerspjrlsz
type-07: addr_test1wrphkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtcl6szpr
type-08: stake_test1uqehkck0lajq8gr28t9uxnuvgcqrc6070x3k9r8048z8y5gssrtvn
type-09: stake_test17rphkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtcljw6kf
```

# Copyright

CC-BY-4.0

[ABNF grammar in annex]: https://raw.githubusercontent.com/cardano-foundation/CIPs/master/CIP-0019/CIP-0019-cardano-addresses.abnf
[base58]: https://tools.ietf.org/id/draft-msporny-base58-01.html
[bech32]: https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki
[BIP-0032]: https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki
[Byron addresses]: #byron-addresses
[CBOR]: https://www.rfc-editor.org/rfc/rfc8949
[CDDL specification of Byron addresses]: https://raw.githubusercontent.com/cardano-foundation/CIPs/master/CIP-0019/CIP-0019-byron-addresses.cddl
[CIP-0005]: https://github.com/cardano-foundation/CIPs/tree/master/CIP-0005/CIP-0005.md
[CIP-1852]: https://github.com/cardano-foundation/CIPs/blob/master/CIP-1852/CIP-1852.md
[derivation path]: #derivation-path
[pointers]: #pointers
[Shelley addresses]: #shelley-addresses
[Stake addresses]: #stake-addresses
1 change: 1 addition & 0 deletions README.md
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Expand Up @@ -23,6 +23,7 @@ The current process is described in details in [CIP1 - "CIP Process"](https://gi
| 14 | [User-facing Asset Fingerprint](https://github.com/cardano-foundation/CIPs/tree/master/CIP-0014) | Draft |
| 15 | [Catalyst Registration Transaction](https://github.com/cardano-foundation/CIPs/tree/master/CIP-0015) | Draft |
| 16 | [Cryptographic Key Serialisation Formats](https://github.com/cardano-foundation/CIPs/tree/master/CIP-0016) | Draft |
| 19 | [Cardano Addresses](https://github.com/cardano-foundation/CIPs/tree/master/CIP-0019) | Draft |
| 1852 | [HD Wallets for Cardano](https://github.com/cardano-foundation/CIPs/tree/master/CIP-1852) | Draft |
| 1853 | [HD Stake Pool Cold Keys](https://github.com/cardano-foundation/CIPs/tree/master/CIP-1853) | Draft |

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