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doc secp256r1 (#8899) 

* Update docs for things related to secp256r1

* docs: update accounts and pubkey documentation

* update table formatting

* Apply suggestions from code review

Co-authored-by: Alessio Treglia <alessio@tendermint.com>

* Apply suggestions from code review

Awesome grammar fixes and style improvements

Co-authored-by: Barrie Byron <barrie.byron@tendermint.com>

* Apply suggestions from code review

Awesome grammar and style improvements.

Co-authored-by: Barrie Byron <barrie.byron@tendermint.com>
Co-authored-by: Alessio Treglia <alessio@tendermint.com>

* hd wallet docs update

* Apply suggestions from code review

Co-authored-by: Barrie Byron <barrie.byron@tendermint.com>

* Update docs/basics/accounts.md

Co-authored-by: Amaury <1293565+amaurym@users.noreply.github.com>

* Update docs/architecture/adr-020-protobuf-transaction-encoding.md

I agree, let's use "and"

* update code snippet links

Co-authored-by: Alessio Treglia <alessio@tendermint.com>
Co-authored-by: Barrie Byron <barrie.byron@tendermint.com>
Co-authored-by: Amaury <1293565+amaurym@users.noreply.github.com>
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4
docs/architecture/adr-020-protobuf-transaction-encoding.md
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@ -288,8 +288,8 @@ and `FileDescriptor`s and returns a boolean result.
### Public Key Encoding
Public keys in the Cosmos SDK implement the `cryptotypes.PubKey` interface.
We propose to use `Any` for protobuf encoding as we are doing with other interfaces (e.g. in `BaseAccount` `PubKey` or `SignerInfo` `PublicKey`).
Following public keys are implemented: secp256k1, ed25519 and multisignature.
We propose to use `Any` for protobuf encoding as we are doing with other interfaces (for example, in `BaseAccount.PubKey` and `SignerInfo.PublicKey`).
The following public keys are implemented: secp256k1, secp256r1, ed25519 and legacy-multisignature.
Ex:

143
docs/basics/accounts.md
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@ -14,7 +14,7 @@ This document describes the in-built accounts system of the Cosmos SDK. {synopsi
In the Cosmos SDK, an _account_ designates a pair of _public key_ `PubKey` and _private key_ `PrivKey`. The `PubKey` can be derived to generate various `Addresses`, which are used to identify users (among other parties) in the application. `Addresses` are also associated with [`message`s](../building-modules/messages-and-queries.md#messages) to identify the sender of the `message`. The `PrivKey` is used to generate [digital signatures](#signatures) to prove that an `Address` associated with the `PrivKey` approved of a given `message`.
To derive `PubKey`s and `PrivKey`s, the Cosmos SDK uses a standard called [BIP32](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki). This standard defines how to build an HD wallet, where a wallet is a set of accounts. At the core of every account, there is a seed, which takes the form of a 12 or 24-words mnemonic. From this mnemonic, it is possible to derive any number of `PrivKey`s using one-way cryptographic function. Then, a `PubKey` can be derived from the `PrivKey`. Naturally, the mnemonic is the most sensitive information, as private keys can always be re-generated if the mnemonic is preserved.
For HD key derivation the Cosmos SDK uses a standard called [BIP32](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki). The BIP32 allows users to create an HD wallet (as specified in [BIP44(https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki)]) - a set of accounts derived from an initial secret seed. A seed is usually created from a 12- or 24-word mnemonic. A single seed can derive any number of `PrivKey`s using a one-way cryptographic function. Then, a `PubKey` can be derived from the `PrivKey`. Naturally, the mnemonic is the most sensitive information, as private keys can always be re-generated if the mnemonic is preserved.
```
Account 0 Account 1 Account 2
@ -56,80 +56,101 @@ To derive `PubKey`s and `PrivKey`s, the Cosmos SDK uses a standard called [BIP32
+-------------------+
```
In the Cosmos SDK, accounts are stored and managed via an object called a [`Keyring`](#keyring).
In the Cosmos SDK, keys are stored and managed by using an object called a [`Keyring`](#keyring).
## Keys, accounts, addresses, and signatures
The principal way of authenticating a user is done using [digital signatures](https://en.wikipedia.org/wiki/Digital_signature). Users sign transactions using their own private key. Signature verification is done with the associated public key. For on-chain signature verification purposes, we store the public key in an `Account` object (alongside other data required for a proper transaction validation).
The Cosmos SDK supports the following digital key schemes for creating digital signatures:
- `secp256k1`, as implemented in the [SDK's `crypto/keys/secp256k1` package](https://github.com/cosmos/cosmos-sdk/blob/v0.42.1/crypto/keys/secp256k1/secp256k1.go).
- `secp256r1`, as implemented in the [SDK's `crypto/keys/secp256r1` package](https://github.com/cosmos/cosmos-sdk/blob/master/crypto/keys/secp256r1/pubkey.go),
- `tm-ed25519`, as implemented in the [SDK `crypto/keys/ed25519` package](https://github.com/cosmos/cosmos-sdk/blob/v0.42.1/crypto/keys/ed25519/ed25519.go). This scheme is supported only for the consensus validation.
| | Address length | Public key length | Used for transaction | Used for consensus |
| | in bytes | in bytes | authentication | (tendermint) |
|--------------+----------------+-------------------+----------------------+--------------------|
| `secp256k1` | 20 | 33 | yes | no |
| `secp256r1` | 32 | 33 | yes | no |
| `tm-ed25519` | -- not used -- | 32 | no | yes |
## Addresses
`Addresses` and `PubKey`s are both public information that identifies actors in the application. `Account` is used to store authentication information. The basic account implementation is provided by a `BaseAccount` object.
Each account is identified using `Address` which is a sequence of bytes derived from a public key. In SDK, we define 3 types of addresses that specify a context where an account is used:
- `AccAddress` identifies users (the sender of a `message`).
- `ValAddress` identifies validator operators.
- `ConsAddress` identifies validator nodes that are participating in consensus. Validator nodes are derived using the **`ed25519`** curve.
These types implement the `Address` interface:
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.42.1/types/address.go#L71-L90
Address construction algorithm is defined in [ADR-28](https://github.com/cosmos/cosmos-sdk/blob/master/docs/architecture/adr-028-public-key-addresses.md).
Here is the standard way to obtain an account address from a `pub` public key:
```go
sdk.AccAddress(pub.Address().Bytes())
```
Of note, the `Marshal()` and `Bytes()` method both return the same raw `[]byte` form of the address. `Marshal()` is required for Protobuf compatibility.
Addresses and public keys are formatted using [Bech32](https://en.bitcoin.it/wiki/Bech32) and implemented by the `String` method. The Bech32 method is the only supported format to use when interacting with a blockchain. The Bech32 human-readable part (Bech32 prefix) is used to denote an address type. Example:
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.42.1/types/address.go#L230-L244
| | Address bech32 Prefix | Pubkey bech32 Prefix |
| ------------------ | --------------------- | -------------------- |
| Accounts | cosmos | cosmospub |
| Validator Operator | cosmosvaloper | cosmosvaloperpub |
| Consensus Nodes | cosmosvalcons | cosmosvalconspub |
### Public Keys
Public keys in Cosmos SDK are defined by `cryptotypes.PubKey` interface. Since public keys are saved in a store, `cryptotypes.PubKey` extends the `proto.Message` interface:
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.42.1/crypto/types/types.go#L8-L17
A compressed format is used for `secp256k1` and `secp256r1` serialization.
- The first byte is a `0x02` byte if the `y`-coordinate is the lexicographically largest of the two associated with the `x`-coordinate.
- Otherwise the first byte is a `0x03`.
This prefix is followed by the `x`-coordinate.
Like `Address`, Bech32 is used to format `PubKey` and for all communication with a blockchain:
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/types/address.go#L579-L729
## Keyring
A `Keyring` is an object that stores and manages accounts. In the Cosmos SDK, a `Keyring` implementation follows the `Keyring` interface:
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/crypto/keyring/keyring.go#L50-L88
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.42.1/crypto/keyring/keyring.go#L51-L89
The default implementation of `Keyring` comes from the third-party [`99designs/keyring`](https://github.com/99designs/keyring) library.
A few notes on the `Keyring` methods:
- `Sign(uid string, payload []byte) ([]byte, tmcrypto.PubKey, error)` strictly deals with the signature of the `payload` bytes. Some preliminary work should be done beforehand to prepare and encode the transaction into a canonical `[]byte` form. Protobuf being not deterministic, it has been decided in [ADR-020](../architecture/adr-020-protobuf-transaction-encoding.md) that the canonical `payload` to sign is the `SignDoc` struct, deterministically encoded using [ADR-027](adr-027-deterministic-protobuf-serialization.md). Note that signature verification is not implemented in the SDK by default, it is deferred to the [`anteHandler`](../core/baseapp.md#antehandler).
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/proto/cosmos/tx/v1beta1/tx.proto#L47-L64
- `Sign(uid string, payload []byte) ([]byte, sdkcrypto.PubKey, error)` strictly deals with the signature of the `payload` bytes. You must prepare and encode the transaction into a canonical `[]byte` form. Because protobuf is not deterministic, it has been decided in [ADR-020](../architecture/adr-020-protobuf-transaction-encoding.md) that the canonical `payload` to sign is the `SignDoc` struct, deterministically encoded using [ADR-027](adr-027-deterministic-protobuf-serialization.md). Note that signature verification is not implemented in the SDK by default, it is deferred to the [`anteHandler`](../core/baseapp.md#antehandler).
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.42.1/proto/cosmos/tx/v1beta1/tx.proto#L47-L64
- `NewAccount(uid, mnemonic, bip39Passwd, hdPath string, algo SignatureAlgo) (Info, error)` creates a new account based on the [`bip44 path`](https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki) and persists it on disk (note that the `PrivKey` is [encrypted with a passphrase before being persisted](https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/crypto/armor.go), it is **never stored unencrypted**). In the context of this method, the `account` and `address` parameters refer to the segment of the BIP44 derivation path (e.g. `0`, `1`, `2`, ...) used to derive the `PrivKey` and `PubKey` from the mnemonic (note that given the same mnemonic and `account`, the same `PrivKey` will be generated, and given the same `account` and `address`, the same `PubKey` and `Address` will be generated). Finally, note that the `NewAccount` method derives keys and addresses using the algorithm specified in the last argument `algo`. Currently, the SDK supports two public key algorithms:
- `NewAccount(uid, mnemonic, bip39Passwd, hdPath string, algo SignatureAlgo) (Info, error)` creates a new account based on the [`bip44 path`](https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki) and persists it on disk. The `PrivKey` is **never stored unencrypted**, instead it is [encrypted with a passphrase](https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/crypto/armor.go) before being persisted. In the context of this method, the key type and sequence number refer to the segment of the BIP44 derivation path (for example, `0`, `1`, `2`, ...) that is used to derive a private and a public key from the mnemonic. Using the same mnemonic and derivation path, the same `PrivKey`, `PubKey` and `Address` is generated. The following keys are supported by the keyring:
- `secp256k1`, as implemented in the [SDK's `crypto/keys/secp256k1` package](https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/crypto/keys/secp256k1/secp256k1.go),
- `ed25519`, as implemented in the [SDK's `crypto/keys/ed25519` package](https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/crypto/keys/ed25519/ed25519.go).
- `secp256k1`
- `ed25519`
- `ExportPrivKeyArmor(uid, encryptPassphrase string) (armor string, err error)` exports a private key in ASCII-armored encrypted format, using the given passphrase. You can then either import it again into the keyring using the `ImportPrivKey(uid, armor, passphrase string)` function, or decrypt it into a raw private key using the `UnarmorDecryptPrivKey(armorStr string, passphrase string)` function.
- `ExportPrivKeyArmor(uid, encryptPassphrase string) (armor string, err error)` exports a private key in ASCII-armored encrypted format using the given passphrase. You can then either import the private key again into the keyring using the `ImportPrivKey(uid, armor, passphrase string)` function or decrypt it into a raw private key using the `UnarmorDecryptPrivKey(armorStr string, passphrase string)` function.
Also see the [`Addresses`](#addresses) section for more information.
## Addresses and PubKeys
`Addresses` and `PubKey`s are both public information that identify actors in the application. There are 3 main types of `Addresses`/`PubKeys` available by default in the Cosmos SDK:
- Addresses and Keys for **accounts**, which identify users (e.g. the sender of a `message`). They are derived using the **`secp256k1`** curve.
- Addresses and Keys for **validator operators**, which identify the operators of validators. They are derived using the **`secp256k1`** curve.
- Addresses and Keys for **consensus nodes**, which identify the validator nodes participating in consensus. They are derived using the **`ed25519`** curve.
| | Address bech32 Prefix | Pubkey bech32 Prefix | Curve | Address byte length | Pubkey byte length |
| ------------------ | --------------------- | -------------------- | ----------- | ------------------- | ------------------ |
| Accounts | cosmos | cosmospub | `secp256k1` | `20` | `33` |
| Validator Operator | cosmosvaloper | cosmosvaloperpub | `secp256k1` | `20` | `33` |
| Consensus Nodes | cosmosvalcons | cosmosvalconspub | `ed25519` | `20` | `32` |
### PubKeys
`PubKey`s used in the Cosmos SDK are Protobuf messages and have the following methods:
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.42.1/crypto/types/types.go#L8-L17
- For `secp256k1` keys, the actual implementation can be found [here](https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/crypto/keys/secp256k1/secp256k1.go).
- For `ed25519` keys, it can be found [here](https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/crypto/keys/ed25519/ed25519.go).
In both case, the actual key (as raw bytes) is the compressed form of the pubkey. The first byte is a `0x02` byte if the `y`-coordinate is the lexicographically largest of the two associated with the `x`-coordinate. Otherwise the first byte is a `0x03`. This prefix is followed with the `x`-coordinate.
Note that in the Cosmos SDK, `Pubkeys` are not manipulated in their raw bytes form. Instead, they are encoded to string using [`Amino`](../core/encoding.md#amino) and [`bech32`](https://en.bitcoin.it/wiki/Bech32). In the SDK, it is done by first calling the `Bytes()` method on the raw `Pubkey` (which applies amino encoding), and then the `ConvertAndEncode` method of `bech32`.
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/types/address.go#L579-L729
### Addresses
The Cosmos SDK comes by default with 3 types of addresses:
- `AccAddress` for accounts.
- `ValAddress` for validator operators.
- `ConsAddress` for validator nodes.
Each of these address types are an alias for an hex-encoded `[]byte` array of length 20. Here is the standard way to obtain an address `aa` from a `Pubkey pub`:
```go
aa := sdk.AccAddress(pub.Address().Bytes())
```
These addresses implement the `Address` interface:
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/types/address.go#L76-L85
Of note, the `Marshal()` and `Bytes()` method both return the same raw `[]byte` form of the address, the former being needed for Protobuf compatibility. Also, the `String()` method is used to return the `bech32` encoded form of the address, which should be the only address format with which end-user interract. Here is an example:
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.40.0-rc3/types/address.go#L235-L249
## Next {hide}