Signing & Key Types

How Signing Works

EVM wallets hash the serialized sign document with Keccak-256 before signing, whereas standard wallets use SHA-256:

signBytes = SignDoc.encode(signDoc)

# Standard
hashedMessage = sha256(signBytes)

# EVM
hashedMessage = keccak256(signBytes)

signature = secp256k1_sign(hashedMessage, privateKey)

The actual elliptic curve operation and signature format (64 bytes: r || s) are identical — only the pre-signing hash function differs.

Public Key Types

CosmJS represents public keys in two forms: Amino JSON and Protobuf. EVM chains use distinct types in each format to signal that the key requires Keccak-based address derivation. Amino JSON:

// Standard
{ type: "tendermint/PubKeySecp256k1", value: "<base64>" }

// EVM
{ type: "os/PubKeyEthSecp256k1", value: "<base64>" }

Protobuf (Any):

// Standard
{ typeUrl: "/cosmos.crypto.secp256k1.PubKey", value: <bytes> }

// EVM
{ typeUrl: "/cosmos.evm.crypto.v1.ethsecp256k1.PubKey", value: <bytes> }

The underlying key bytes are identical (33-byte compressed secp256k1). The different type identifiers tell the chain how to derive the address from the key.

The Algo Identifier

The AccountData.algo field distinguishes EVM accounts from standard ones. Two naming conventions exist in the ecosystem:

"eth_secp256k1" — used by Keplr wallet, CosmJS wallets, and some chains
"ethsecp256k1" — used by Evmos, Cronos, and other EVM-compatible chains

CosmJS handles both through the isEthereumSecp256k1Account() utility:

import { isEthereumSecp256k1Account } from "@cosmjs/amino";

const [account] = await wallet.getAccounts();
if (isEthereumSecp256k1Account(account)) {
  // EVM-compatible account
}

The getAminoPubkey() function uses this check to select the correct encoding automatically. This is what SigningStargateClient calls internally when building transactions:

import { getAminoPubkey } from "@cosmjs/amino";

const pubkey = getAminoPubkey(account);
// Returns EthSecp256k1Pubkey or Secp256k1Pubkey based on account.algo

CosmJS

Concepts

Guides

API Reference

How Signing Works

Public Key Types

The Algo Identifier

​How Signing Works

​Public Key Types

​The Algo Identifier

How Signing Works

Public Key Types

The Algo Identifier