ethereum-cryptography

This npm package contains all the cryptographic primitives normally used when developing Javascript/TypeScript applications and tools for Ethereum.

Pure Javascript implementations of all the primitives are included, so it can be used out of the box for web applications and libraries.

In Node, it takes advantage of the built-in and N-API based implementations whenever possible.

The cryptographic primitives included are:

• Pseudorandom number generation
• Keccak
• Scrypt
• PBKDF2
• SHA-256
• RIPEMD-160
• BLAKE2b
• AES
• Secp256k1
• Hierarchical Deterministic keys derivation
• Seed recovery phrases

Installation

Via npm:

$ npm install ethereum-cryptography

Via yarn:

$ yarn add ethereum-cryptography

Usage

This package has no single entry-point, but submodule for each cryptographic primitive. Read each primitive's section of this document to learn how to use them.

The reason for this is that importing everything from a single file will lead to huge bundles when using this package for the web. This could be avoided through tree-shaking, but the possibility of it not working properly on one of the supported bundlers is too high.

Pseudorandom number generation submodule

The random submodule has functions to generate cryptographically strong pseudo-random data in synchronous and asynchronous ways.

In Node, this functions are backed by crypto.randomBytes.

In the browser, crypto.getRandomValues is used. If not available, this module won't work, as that would be insecure.

Function types

function getRandomBytes(bytes: number): Promise<Buffer>;

function getRandomBytesSync(bytes: number): Buffer;

Example usage

const { getRandomBytesSync } = require("ethereum-cryptography/random");

console.log(getRandomBytesSync(32).toString("hex"));

Keccak submodule

The keccak submodule has four functions that implement different variations of the Keccak hashing algorithm. These are keccak224, keccak256, keccak384, and keccak512.

Function types

function keccak224(msg: Buffer): Buffer;

function keccak256(msg: Buffer): Buffer;

function keccak384(msg: Buffer): Buffer;

function keccak512(msg: Buffer): Buffer;

Example usage

const { keccak256 } = require("ethereum-cryptography/keccak");

console.log(keccak256(Buffer.from("Hello, world!", "ascii")).toString("hex"));

Scrypt submodule

The scrypt submodule has two functions implementing the Scrypt key derivation algorithm in synchronous and asynchronous ways. This algorithm is very slow, and using the synchronous version in the browser is not recommended, as it will block its main thread and hang your UI.

Password encoding

Encoding passwords is a frequent source of errors. Please read these notes before using this submodule.

Function types

function scrypt(password: Buffer, salt: Buffer, n: number, p: number, r: number, dklen: number): Promise<Buffer>;

function scryptSync(password: Buffer, salt: Buffer, n: number, p: number, r: number, dklen: number): Buffer;

Example usage

const { scryptSync } = require("ethereum-cryptography/scrypt");

console.log(
  scryptSync(
    Buffer.from("ascii password", "ascii"),
    Buffer.from("salt", "hex"),
    16,
    1,
    1,
    64
  ).toString("hex")
);

PBKDF2 submodule

The pbkdf2 submodule has two functions implementing the PBKDF2 key derivation algorithm in synchronous and asynchronous ways. This algorithm is very slow, and using the synchronous version in the browser is not recommended, as it will block its main thread and hang your UI.

Password encoding

Encoding passwords is a frequent source of errors. Please read these notes before using this submodule.

Supported digests

In Node this submodule uses the built-in implementation and supports any digest returned by crypto.getHashes.

In the browser, it is tested to support at least sha256, the only digest normally used with pbkdf2 in Ethereum. It may support more.

Function types

function pbkdf2(password: Buffer, salt: Buffer, iterations: number, keylen: number, digest: string): Promise<Buffer>;

function pbkdf2Sync(password: Buffer, salt: Buffer, iterations: number, keylen: number, digest: string): Buffer;

Example usage

const { pbkdf2Sync } = require("ethereum-cryptography/pbkdf2");

console.log(
  pbkdf2Sync(
    Buffer.from("ascii password", "ascii"),
    Buffer.from("salt", "hex"),
    4096,
    32,
    'sha256'
  ).toString("hex")
);

SHA-256 submodule

The sha256 submodule contains a single function implementing the SHA-256 hashing algorithm.

Function types

function sha256(msg: Buffer): Buffer;

Example usage

const { sha256 } = require("ethereum-cryptography/sha256");

console.log(sha256(Buffer.from("message", "ascii")).toString("hex"));

RIPEMD-160 submodule

The ripemd160 submodule contains a single function implementing the RIPEMD-160 hashing algorithm.

Function types

function ripemd160(msg: Buffer): Buffer;

Example usage

const { ripemd160 } = require("ethereum-cryptography/ripemd160");

console.log(ripemd160(Buffer.from("message", "ascii")).toString("hex"));

BLAKE2b submodule

The blake2b submodule contains a single function implementing the BLAKE2b non-keyed hashing algorithm.

Function types

function blake2b(input: Buffer, outputLength = 64): Buffer;

Example usage

const { blake2b } = require("ethereum-cryptography/blake2b");

console.log(blake2b(Buffer.from("message", "ascii")).toString("hex"));

AES submodule

The aes submodule contains encryption and decryption functions implementing the Advanced Encryption Standard algorithm.

Encrypting with passwords

AES is not supposed to be used directly with a password. Doing that will compromise your users' security.

The key parameters in this submodule are meant to be strong cryptographic keys. If you want to obtain such a key from a password, please use a key derivation function like pbkdf2 or scrypt.

Operation modes

This submodule works with different block cipher modes of operation. If you are using this module in a new application, we recommend using the default.

While this module may work with any mode supported by OpenSSL, we only test it with aes-128-ctr, aes-128-cbc, and aes-256-cbc. If you use another module a warning will be printed in the console.

We only recommend using aes-128-cbc and aes-256-cbc to decrypt already encrypted data.

Padding plaintext messages

Some operation modes require the plaintext message to be a multiple of 16. If that isn't the case, your message has to be padded.

By default, this module automatically pads your messages according to PKCS#7. Note that this padding scheme always adds at least 1 byte of padding. If you are unsure what anything of this means, we strongly recommend you to use the defaults.

If you need to encrypt without padding or want to use another padding scheme, you can disable PKCS#7 padding by passing false as the last argument and handling padding yourself. Note that if you do this and your operation mode requires padding, encrypt will throw if your plaintext message isn't a multiple of 16.

This option is only present to enable the decryption of already encrypted data. To encrypt new data, we recommend using the default.

How to use the IV parameter

The iv parameter of the encrypt function must be unique, or the security of the encryption algorithm can be compromissed.

You can generate a new iv using the random module.

Note that to decrypt a value, you have to provide the same iv used to encrypt it.

How to handle errors with this module

Sensitive information can be leaked via error messages when using this module. To avoid this, you should make sure that the errors you return don't contain the exact reason for the error. Instead, errors must report general encryption/decryption failures.

Note that implementing this can mean catching all errors that can be thrown when calling on of this module's functions, and just throwing a new generic exception.

Function types

function encrypt(msg: Buffer, key: Buffer, iv: Buffer, mode = "aes-128-ctr", pkcs7PaddingEnabled = true): Buffer;

function decrypt(cypherText: Buffer, key: Buffer, iv: Buffer, mode = "aes-128-ctr", pkcs7PaddingEnabled = true): Buffer

Example usage

const { encrypt } = require("ethereum-cryptography/aes");

console.log(
  encrypt(
    Buffer.from("message", "ascii"),
    Buffer.from("2b7e151628aed2a6abf7158809cf4f3c", "hex"),
    Buffer.from("f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff", "hex")
  ).toString("hex")
);

Secp256k1 submodule

The secp256k1 submodule provides a library for elliptic curve operations on the curve Secp256k1.

It has the exact same API than the version 4.x of the secp256k1 module from cryptocoinjs, with two added function to create private keys.

Creating private keys

Secp256k1 private keys need to be cryptographycally secure random numbers with certain caracteristics. If this is not the case, the security of Secp256k1 is compromissed.

We strongly recommend to use this module to create new private keys.

Function types

Functions to create private keys:

function createPrivateKey(): Promise<Uint8Array>;

function function createPrivateKeySync(): Uint8Array;

For the rest of the functions, pleasse read secp256k1's documentation.

Example usage

const { createPrivateKeySync, ecdsaSign } = require("ethereum-cryptography/secp256k1");

const msgHash = Buffer.from(
  "82ff40c0a986c6a5cfad4ddf4c3aa6996f1a7837f9c398e17e5de5cbd5a12b28",
  "hex"
);

const privateKey = createPrivateKeySync();

console.log(Buffer.from(ecdsaSign(msgHash, privateKey).signature).toString("hex"));

Hierarchical Deterministic keys submodule

The hdkey submodule provides a library for keys derivation according to BIP32.

It has almost the exact same API than the version 1.x of hdkey from cryptocoinjs, but it's backed by this package's primitives, and has built-in TypeScript types. Its only difference is that it has to be be used with a named import.

Function types

This module exports a single class whose type is

class HDKey {
  public static HARDENED_OFFSET: number;
  public static fromMasterSeed(seed: Buffer, versions: Versions): HDKey;
  public static fromExtendedKey(base58key: string, versions: Versions): HDKey;
  public static fromJSON(json: { xpriv: string }): HDKey;

  public versions: Versions;
  public depth: number;
  public index: number;
  public chainCode: Buffer | null;
  public privateKey: Buffer | null;
  public publicKey: Buffer | null;
  public fingerprint: number;
  public parentFingerprint: number;
  public pubKeyHash: Buffer | undefined;
  public identifier: Buffer | undefined;
  public privateExtendedKey: string;
  public publicExtendedKey: string;

  private constructor(versios: Versions);
  public derive(path: string): HDKey;
  public deriveChild(index: number): HDKey;
  public sign(hash: Buffer): Buffer;
  public verify(hash: Buffer, signature: Buffer): boolean;
  public wipePrivateData(): this;
  public toJSON(): { xpriv: string; xpub: string };
}

interface Versions {
  private: number;
  public: number;
}

Example usage

const { HDKey } = require("ethereum-cryptography/hdkey");

const seed = "fffcf9f6f3f0edeae7e4e1dedbd8d5d2cfccc9c6c3c0bdbab7b4b1aeaba8a5a29f9c999693908d8a8784817e7b7875726f6c696663605d5a5754514e4b484542";
const hdkey = HDKey.fromMasterSeed(Buffer.from(seed, "hex"));
const childkey = hdkey.derive("m/0/2147483647'/1");

console.log(childkey.privateExtendedKey);

Seed recovery phrases

The bip39 submodule provides functions to generate, validate and use seed recovery phrases according to BIP39.

Function types

function generateMnemonic(wordlist: string[], strength: number = 128): string;

function mnemonicToEntropy(mnemonic: string, wordlist: string[]): Buffer;

function entropyToMnemonic(entropy: Buffer, wordlist: string[]): string;

function validateMnemonic(mnemonic: string, wordlist: string[]): boolean;

async function mnemonicToSeed(mnemonic: string, passphrase: string = ""): Promise<Buffer>;

function mnemonicToSeedSync(mnemonic: string, passphrase: string = ""): Buffer;

Word lists

This submodule also contains the word lists defined by BIP39 for Czech, English, French, Italian, Japanese, Korean, Simplified and Traditional Chinese, and Spanish. These are not imported by default, as that would increase bundle sizes too much. Instead, you should import and use them explicitly.

The word lists are exported as a wordlist variable in each of these submodules:

• ethereum-cryptography/bip39/wordlists/czech.js

• ethereum-cryptography/bip39/wordlists/english.js

• ethereum-cryptography/bip39/wordlists/french.js

• ethereum-cryptography/bip39/wordlists/italian.js

• ethereum-cryptography/bip39/wordlists/japanese.js

• ethereum-cryptography/bip39/wordlists/korean.js

• ethereum-cryptography/bip39/wordlists/simplified-chinese.js

• ethereum-cryptography/bip39/wordlists/spanish.js

• ethereum-cryptography/bip39/wordlists/traditional-chinese.js

Example usage

const { generateMnemonic } = require("ethereum-cryptography/bip39");
const { wordlist } = require("ethereum-cryptography/bip39/wordlists/english");

console.log(generateMnemonic(wordlist));

Browser usage

This package works with all the major Javascript bundlers. It is tested with webpack, Rollup, Parcel, and Browserify.

Rollup setup

Using this library with Rollup requires the following plugins:

• @rollup/plugin-commonjs
• @rollup/plugin-json
• @rollup/plugin-node-resolve
• rollup-plugin-node-builtins
• rollup-plugin-node-globals

These can be used by setting your plugins array like this:

  plugins: [
    commonjs(),
    json(),
    nodeGlobals(),
    nodeBuiltins(),
    resolve({
      browser: true,
      preferBuiltins: false,
    }),
  ]

Missing cryptographic primitives

This package intentionally excludes the the cryptographic primitives necessary to implement the following EIPs:

• EIP 196: Precompiled contracts for addition and scalar multiplication on the elliptic curve alt_bn128
• EIP 197: Precompiled contracts for optimal ate pairing check on the elliptic curve alt_bn128
• EIP 198: Big integer modular exponentiation
• EIP 152: Add Blake2 compression function F precompile

Feel free to open an issue if you want this decision to be reconsidered, or if you found another primitive that is missing.

Security audit

This library has been audited by Trail of Bits. You can see the results of the audit and the changes implemented as a result of it in audit/.

License

ethereum-cryptography is released under the MIT License.