eciesjs

Elliptic Curve Integrated Encryption Scheme for secp256k1/curve25519 in TypeScript.

This is the JavaScript/TypeScript version of eciespy with a built-in class-like secp256k1/curve25519 API.

You can learn the details in DETAILS.md.

Install

1npm install eciesjs

We recommend using the latest Node runtime although it's still possible to install on old versions (as long as 16+).

For security, see Security.

Quick Start

1import { PrivateKey, decrypt, encrypt } from "eciesjs";
2
3const sk = new PrivateKey();
4const data = Buffer.from("hello world🌍");
5const decrypted = decrypt(sk.secret, encrypt(sk.publicKey.toBytes(), data));
6console.log(Buffer.from(decrypted).toString());

Or run the example code:

1$ pnpm install && pnpm build && cd example/runtime && pnpm install && node main.js
2hello world🌍

See Configuration to control with more granularity.

This library also supports multiple platforms (browser, node, bun/deno, react native), see Multi-platform Support.

Sponsors

API

encrypt(receiverRawPK: string | Uint8Array, data: Uint8Array): Buffer

Parameters:

• receiverRawPK - Receiver's public key, hex string or Uint8Array
• data - Data to encrypt

Returns: Buffer

decrypt(receiverRawSK: string | Uint8Array, data: Uint8Array): Buffer

Parameters:

• receiverRawSK - Receiver's private key, hex string or Uint8Array
• data - Data to decrypt

Returns: Buffer

PrivateKey

• Methods

1static fromHex(hex: string, curve?: EllipticCurve): PrivateKey;
2constructor(secret?: Uint8Array, curve?: EllipticCurve);
3toHex(): string;
4encapsulate(pk: PublicKey, compressed?: boolean): Uint8Array;
5multiply(pk: PublicKey, compressed?: boolean): Uint8Array;
6equals(other: PrivateKey): boolean;

• Properties

1get secret(): Buffer;
2readonly publicKey: PublicKey;

PublicKey

• Methods

1static fromHex(hex: string, curve?: EllipticCurve): PublicKey;
2constructor(data: Uint8Array, curve?: EllipticCurve);
3toBytes(compressed?: boolean): Uint8Array;
4toHex(compressed?: boolean): string;
5decapsulate(sk: PrivateKey, compressed?: boolean): Uint8Array;
6equals(other: PublicKey): boolean;

• Properties

1/** @deprecated - use `PublicKey.toBytes(false)` instead. You may also need `Buffer.from`. */
2get uncompressed(): Buffer;
3/** @deprecated - use `PublicKey.toBytes()` instead. You may also need `Buffer.from`. */
4get compressed(): Buffer;

Configuration

Following configurations are available.

• Elliptic curve: secp256k1 or curve25519 (x25519/ed25519)
• Ephemeral key format in the payload: compressed or uncompressed (only for secp256k1)
• Shared elliptic curve key format in the key derivation: compressed or uncompressed (only for secp256k1)
• Symmetric cipher algorithm: AES-256-GCM or XChaCha20-Poly1305
• Symmetric nonce length: 12 or 16 bytes (only for AES-256-GCM)

For compatibility, make sure different applications share the same configuration.

1export type EllipticCurve = "secp256k1" | "x25519" | "ed25519";
2export type SymmetricAlgorithm = "aes-256-gcm" | "xchacha20";
3export type NonceLength = 12 | 16;
4
5class Config {
6  ellipticCurve: EllipticCurve = "secp256k1";
7  isEphemeralKeyCompressed: boolean = false;
8  isHkdfKeyCompressed: boolean = false;
9  symmetricAlgorithm: SymmetricAlgorithm = "aes-256-gcm";
10  symmetricNonceLength: NonceLength = 16;
11}
12
13export const ECIES_CONFIG = new Config();

Elliptic curve configuration

On ellipticCurve = "x25519" or ellipticCurve = "ed25519", x25519 (key exchange function on curve25519) or ed25519 (signature algorithm on curve25519) will be used for key exchange instead of secp256k1.

In this case, the payload would always be: 32 Bytes + Ciphered regardless of isEphemeralKeyCompressed.

If you don't know how to choose between x25519 and ed25519, just use the dedicated key exchange function x25519 for efficiency.

Because any 32-byte data is a valid curve25519 public key, the payload would seem random. This property is excellent for circumventing censorship by adversaries.

Secp256k1-specific configuration

On isEphemeralKeyCompressed = true, the payload would be: 33 Bytes + Ciphered instead of 65 Bytes + Ciphered.

On isHkdfKeyCompressed = true, the hkdf key would be derived from ephemeral public key (compressed) + shared public key (compressed) instead of ephemeral public key (uncompressed) + shared public key (uncompressed).

Symmetric cipher configuration

On symmetricAlgorithm = "xchacha20", plaintext data would be encrypted with XChaCha20-Poly1305.

On symmetricNonceLength = 12, the nonce of AES-256-GCM would be 12 bytes. XChaCha20-Poly1305's nonce is always 24 bytes regardless of symmetricNonceLength.

Which configuration should I choose?

For compatibility with other ecies libraries, start with the default (secp256k1 with AES-256-GCM).

For speed and security, pick x25519 with XChaCha20-Poly1305.

If you know exactly what you are doing, configure as you wish or build your own ecies logic with this library.

Multi-platform Support

	Fully Supported
Node	✅
Bun	✅
Deno	⚠️ (only aes)
Browser	✅
React Native	✅

Via @ecies/ciphers, node:crypto's native implementation of AES-256-GCM and XChaCha20-Poly1305 is chosen if available.

Browser

This library is browser-friendly, check the example/browser directory for details. The online demo is hosted here.

Currently it's necessary to polyfill Buffer for backward compatibility. From v0.5.0, it can run in browsers as is.

If you want a WASM version to run directly in modern browsers or on some blockchains, you can also try ecies-wasm.

Bun/Deno

For bun/deno, see example/runtime. There are some limitations currently, mentioned in @ecies/ciphers:

• chacha20-poly1305's pure JS implementation is used on bun (node:crypto's chacha20-poly1305 is not available due to lack of implementation);
• chacha20-poly1305 does not work on deno. If you found such a problem, try to upgrade deno to the latest version (no guarantee whether it works though).

React Native

See the React Native demo.

Security

To mitigate security risks, such as supply chain attacks and zero-day vulnerabilities, we only use node:crypto and these audited dependencies:

• noble-curves
• noble-hashes
• noble-ciphers

Every release is built on GitHub Actions with provenance.

This library is fully auditable as well. We're seeking funding for a professional third-party security audit to verify implementation and identify potential vulnerabilities.

If you rely on this library or value secure open-source cryptography, please consider donating to help fund this audit.

Changelog

See CHANGELOG.md.