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Prerequisite Readings

Cosmos SDK Accounts

Learn about account structure in Cosmos SDK

Ethereum Accounts

Understand Ethereum account model

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Creating Accounts

To create one account you can either create a private key, a keystore file (a private key protected by a password), or a mnemonic phrase (a string of words that can access multiple private keys). Aside from having different security features, the biggest difference between each of these is that a private key or keystore file only creates one account. Creating a mnemonic phrase gives you control of many accounts, all accessible with that same phrase. Cosmos blockchains, like the Cosmos Hub, support creating accounts with mnemonic phrases, otherwise known as hierarchical deterministic key generation (HD keys). This allows the user to create accounts on multiple blockchains without having to manage multiple secrets. HD keys generate addresses by taking the mnemonic phrase and combining it with a piece of information called a derivation path. Blockchains can differ in which derivation path they support. To access all accounts from an mnemonic phrase on a blockchain, it is therefore important to use that blockchain’s specific derivation path.

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Representing Accounts

The terms “account” and “address” are often used interchangeably to describe crypto wallets. In the Cosmos SDK, an account designates a pair of public key (PubKey) and private key (PrivKey). The derivation path defines what the private key, public key, and address would be. The PubKey can be derived to generate various addresses in different formats, which are used to identify users (among other parties) in the application. A common address form for Cosmos chains is the bech32 format (e.g. cosmos1...). Addresses are also associated with messages to identify the sender of the message. The PrivKey is used to generate digital signatures to prove that an address associated with the PrivKey approved of a given message. The proof is performed by applying a cryptographic scheme to the PrivKey, known as Elliptic Curve Digital Signature Algorithm (ECDSA), to generate a PubKey that is compared with the address in the message.

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EVM Accounts

Cosmos EVM defines its own custom Account type to implement a HD wallet that is compatible with Ethereum type addresses. It uses Ethereum’s ECDSA secp256k1 curve for keys (eth_secp265k1) and satisfies the EIP84 for full BIP44 paths. This cryptographic curve is not to be confused with Bitcoin’s ECDSA secp256k1 curve. The root HD path for EVM-based accounts is m/44'/60'/0'/0. It is recommended to use the Coin type 60 to support Ethereum type accounts, unlike many other Cosmos chains that use Coin type 118 (list of coin types The custom Cosmos EVM EthAccount satisfies the AccountI interface from the Cosmos SDK auth module and includes additional fields that are required for Ethereum type addresses: 
// EthAccountI represents the interface of an EVM compatible accounttype EthAccountI interface {    authtypes.AccountI    // EthAddress returns the ethereum Address representation of the AccAddress    EthAddress() common.Address    // CodeHash is the keccak256 hash of the contract code (if any)    GetCodeHash() common.Hash    // SetCodeHash sets the code hash to the account fields    SetCodeHash(code common.Hash) error    // Type returns the type of Ethereum Account (EOA or Contract)    Type() int8}
For more information on Ethereum accounts head over to the x/evm module.

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Addresses and Public Keys

BIP-0173 defines a new format for segregated witness output addresses that contains a human-readable part that identifies the Bech32 usage. There are 3 main types of HRP for the Addresses/PubKeys available by default on the Cosmos EVM:
Purpose: Identify users (e.g., transaction senders)
  • Curve: eth_secp256k1
  • Address Prefix: cosmos
  • Pubkey Prefix: cosmospub
  • Address Length: 20 bytes
  • Pubkey Length: 33 bytes (compressed)

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Address formats for clients

EthAccount can be represented in both Bech32 (e.g. cosmos1...) and hex (0x...) formats for Ethereum’s Web3 tooling compatibility.
The Bech32 format is the default for Cosmos-SDK queries and transactions, while the hex format is used for Ethereum compatibility.
cosmos1z3t55m0l9h0eupuz3dp5t5cypyv674jj7mz2jw

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Address conversion

The appd debug addr <address> can be used to convert an address between hex and bech32 formats: 
$ appd debug addr cosmos1z3t55m0l9h0eupuz3dp5t5cypyv674jj7mz2jw

Address: [20 87 74 109 255 45 223 158 7 130 139 67 69 211 4 9 25 175 86 82]
Address (hex): 14574A6DFF2DDF9E07828B4345D3040919AF5652
Bech32 Acc: cosmos1z3t55m0l9h0eupuz3dp5t5cypyv674jj7mz2jw
Bech32 Val: cosmosvaloper1z3t55m0l9h0eupuz3dp5t5cypyv674jjn4d6nn

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Key output

The Cosmos SDK Keyring output (i.e appd keys) only supports addresses and public keys in Bech32 format.
We can use the keys show command with the flag --bech <type> to obtain different address formats: 
$ appd keys show dev0 --bech acc

- name: dev0
  type: local
  address: cosmos1z3t55m0l9h0eupuz3dp5t5cypyv674jj7mz2jw
  pubkey: '{"@type":"/ethermint.crypto.v1.ethsecp256k1.PubKey","key":"AsV5oddeB+hkByIJo/4lZiVUgXTzNfBPKC73cZ4K1YD2"}'
  mnemonic: ""

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Querying an Account

You can query an account address using CLI, gRPC, REST, or JSON-RPC: 
# NOTE: the --output (-o) flag defines the output format
appd q auth account $(appd keys show dev0 -a) -o text

'@type': /ethermint.types.v1.EthAccount
base_account:
  account_number: "0"
  address: cosmos1z3t55m0l9h0eupuz3dp5t5cypyv674jj7mz2jw
  pub_key:
    '@type': /ethermint.crypto.v1.ethsecp256k1.PubKey
    key: AsV5oddeB+hkByIJo/4lZiVUgXTzNfBPKC73cZ4K1YD2
  sequence: "1"
code_hash: 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470
For JSON-RPC methods, see eth_accounts and personal_listAccounts documentation.