swift-argon2

An arm64-compatible Swift Package for Argon2 password hashing and key derivation.

Why this package?

Every existing Swift Argon2 package chains to P-H-C/phc-winner-argon2 as a remote SPM dependency using .branch("master"). That upstream package includes blamka-round-opt.h, which unconditionally includes <emmintrin.h> (SSE2). On arm64 — iOS devices and Apple Silicon simulators — Clang cannot load the _Builtin_intrinsics.intel.sse2 module, producing a fatal build error:

Module '_Builtin_intrinsics.intel.sse2' requires feature 'x86'

This package fixes the problem by vendoring the argon2 C reference sources directly (ref.c, not opt.c) and never placing SSE2 headers anywhere in the include tree. It has zero transitive dependencies, so SPM resolution is instant and hermetic.

Requirements

Platform	Minimum version
iOS	16.0
macOS	13.0
tvOS	16.0
watchOS	9.0

Swift 5.7 or later. Swift Package Manager only.

Installation

// Package.swift
.package(url: "https://github.com/dugleelabs/swift-argon2", from: "1.0.0")

// Target dependency
.product(name: "Argon2", package: "swift-argon2")

Usage

import Argon2

// Derive a 32-byte key from a password (production parameters)
// Always call from a background thread — this is CPU-intensive.
let key = try await Task.detached(priority: .userInitiated) {
    try Argon2.hash(
        password: Data("my-password".utf8),
        salt:     saltData,          // 32 random bytes, stored server-side
        iterations:  3,
        memory:      524_288,        // 512 MiB in KiB
        parallelism: 4,
        outputLength: 32,
        variant: .id                 // Argon2id — recommended
    )
}.value

API

public enum Argon2 {

    public enum Variant { case d, i, id }

    public enum Error: Swift.Error {
        case hashingFailed(code: Int32, message: String)
    }

    /// Derives a fixed-length key from a password.
    public static func hash(
        password: Data,
        salt: Data,
        iterations: Int,
        memory: Int,          // KiB
        parallelism: Int,
        outputLength: Int = 32,
        variant: Variant = .id
    ) throws -> Data
}

Parameter guidance

Parameter	Recommended	Notes
variant	.id	RFC 9106 and OWASP default; use .i only if side-channel resistance required without GPU resistance
iterations	3	Increase to raise time cost; protocol-defined — don't change unilaterally
memory	524_288	512 MiB; reduces to fit device constraints only with protocol agreement
parallelism	4	Should match available CPU threads
outputLength	32	32 bytes = 256-bit key
salt	32 random bytes	Generate with var salt = [UInt8](repeating: 0, count: 32); SecRandomCopyBytes(kSecRandomDefault, 32, &salt)

Cryptographic notes

• Output is byte-identical to Python argon2.low_level.hash_secret_raw at identical parameters — both call the same C reference implementation.
• This package uses ref.c (reference compression function) rather than opt.c (x86 SSE2-optimised). There is no performance difference on arm64 (the optimised path cannot run there); on x86 the reference path is measurably slower, which is an accepted trade-off for arm64 compatibility.
• Argon2 version 1.3 (0x13) is hardcoded. Version 1.0 is not supported.
• For background reading: RFC 9106, OWASP Password Storage Cheat Sheet.

Vendored sources

The phc-winner-argon2 C sources are vendored at commit f57e61e19229e23c4445b85494dbf7c07de721cb (2021-06-25) under CC0 1.0 / Apache-2.0. See Sources/CArgon2/VENDORED.md for the full file list and update procedure.

Licence

This package is released under the Apache License 2.0.

The bundled C sources (Sources/CArgon2/) are copyright their original authors (Daniel Dinu, Dmitry Khovratovich, Jean-Philippe Aumasson, Samuel Neves) and are available under CC0 1.0 Universal / Apache License 2.0.