zig-crypto

Portable cryptographic primitives in Zig with C FFI -- SHA-256, HMAC-SHA-256, AES-CBC, PBKDF2, ECDH P-256, Ed25519, and CSPRNG.

License: Zlib OR MIT

Why

A minimal, zero-dependency crypto library that compiles to a static C library from Zig. No OpenSSL, no CommonCrypto, no system dependencies. Provides the cryptographic primitives needed by CTAP2 PIN protocol, Sparkle update signing, and general-purpose credential management.

Features

• SHA-256: Single-shot and incremental hashing, hex output
• HMAC-SHA-256: RFC 4231-conformant message authentication
• AES-128-CBC / AES-256-CBC: Encrypt/decrypt with PKCS#7 padding
• AES-256-CBC raw: No-padding mode for CTAP2 PIN protocol
• PBKDF2-SHA1: RFC 6070-conformant key derivation
• ECDH P-256: Key generation and shared secret derivation
• Ed25519: Key generation, signing, verification
• CSPRNG: OS-backed cryptographically secure random bytes
• C FFI: 19 exported functions
• Property-based tests: Roundtrip tests for SHA-256, AES, ECDH, Ed25519

Requirements

• Zig 0.15.2+
• No platform-specific dependencies (pure Zig std.crypto)

Architecture

graph TD
    A[Application] -->|C FFI| B[ffi.zig<br/>19 exported functions]
    B --> C[sha256.zig]
    B --> D[hmac.zig]
    B --> E[aes.zig]
    B --> F[pbkdf2.zig]
    B --> G[ecdh.zig]
    B --> H[ed25519.zig]
    B --> I[random.zig]
    C --> Z[std.crypto]
    D --> Z
    E --> Z
    F --> Z
    G --> Z
    H --> Z
    I --> Z

Loading

Build

zig build -Doptimize=ReleaseFast   # static library
zig build test                      # unit tests
zig build test-pbt                  # property-based tests

With just: just test-all, just build, just info.

Platform Support

Platform	Status	Notes
macOS (arm64/x86_64)	Tested	No frameworks needed
Linux (x86_64/arm64)	Supported	No system libraries needed
Cross-compilation	Supported	Pure Zig, no platform dependencies

C API Reference

Header: include/zig_crypto.h. All functions are thread-safe and stateless.

Function	Returns	Description
zig_crypto_sha256	void	SHA-256 hash (out: 32 bytes)
zig_crypto_sha256_hex	size_t (64)	SHA-256 as hex (out: 64 bytes)
zig_crypto_hmac_sha256	void	HMAC-SHA-256 (out: 32 bytes)
zig_crypto_aes128_cbc_encrypt	int	AES-128-CBC encrypt, PKCS#7
zig_crypto_aes128_cbc_decrypt	int	AES-128-CBC decrypt, PKCS#7
zig_crypto_aes256_cbc_encrypt	int	AES-256-CBC encrypt, PKCS#7
zig_crypto_aes256_cbc_decrypt	int	AES-256-CBC decrypt, PKCS#7
zig_crypto_aes256_cbc_encrypt_raw	int	AES-256-CBC no padding (CTAP2)
zig_crypto_aes256_cbc_decrypt_raw	int	AES-256-CBC no unpadding (CTAP2)
zig_crypto_pbkdf2_sha1	void	PBKDF2-HMAC-SHA1 key derivation
zig_crypto_p256_generate	int (0/-1)	Generate P-256 key pair
zig_crypto_p256_ecdh	int (0/-1)	ECDH shared secret
zig_crypto_ed25519_generate	void	Generate Ed25519 key pair
zig_crypto_ed25519_from_seed	int (0/-1)	Deterministic key from seed
zig_crypto_ed25519_sign	int (0/-1)	Sign message (sig: 64 bytes)
zig_crypto_ed25519_verify	bool	Verify signature
zig_crypto_random	bool	Fill with secure random bytes

Integration

git submodule add https://github.com/Jesssullivan/zig-crypto.git vendor/crypto
cd vendor/crypto && zig build -Doptimize=ReleaseFast

Link: -lzig-crypto. Include: #include "zig_crypto.h".

License

Dual-licensed under Zlib and MIT. Choose whichever you prefer.