LuaNacha (NaCl with Chacha20) is a small Lua cryptographic library wrapping the excellent Monocypher cryptographic C library by Loup Vaillant - http://loup-vaillant.fr/projects/monocypher/ and https://github.com/LoupVaillant/Monocypher
The Monocypher library is included here (currently version 2.0.5)
Monocypher is itself heavily based on the NaCl crypto library by Daniel Bernstein and Tanja Lange.
Major features and differences with the NaCl library:
- Authenticated encryption with Chacha20 stream encryption (more precisely Xchacha20, ie. Chacha with a 24-byte nonce) and Poly1305 MAC,
- Curve25519-based key exchange and public key encryption,
- Blake2b hash function,
- Ed25519-based signature function using Blake2b hash instead of sha512,
- Argon2i, a modern key derivation function based on Blake2b. Like scrypt, it is designed to be expensive in both CPU and memory.
The complete documentation of the Monocypher library is available at http://loup-vaillant.fr/projects/monocypher/manual
Note: As of August 2017, Monocypher is deemed to be production-ready. (See section "Current state" at http://loup-vaillant.fr/projects/monocypher/)
The Lua wrapper
It includes an interface to an OS random generator (for the moment only based on /dev/urandom and tested on Linux)
The functions keep as much as possible the same name as in Monocypher (without the "crypto_" prefix) and the same parameter order.
LuaNacha API summary:
randombytes(n) return a string containing n random bytes --- Authenticated encryption lock(key, nonce, plain [, prefix]) => crypted authenticated encryption using Xchacha20 and a Poly1305 MAC key must be a 32-byte string nonce must be a 24-byte string plain is the text to encrypt as a string prefix is an optional string. If it is provided, it is prepended to the encrypted text. The prefix can be use for example to store the nonce, and avoid extra string allocation and copying in Lua applications. The prefix defaults to the empty string. Return the encrypted text as a string. The encrypted text includes the 16-byte MAC. So #crypted == #plain + 16 + #prefix Note: the prefix is not an "additional data" in the AEAD sense. The MAC is computed over only the encrypted text. It does not include the prefix. unlock(key, nonce, crypted [, offset]) => plain authenticated decryption - verification of the Poly1305 MAC and decryption with Xcahcha20. key must be a 32-byte string nonce must be a 24-byte string crypted is the text to decrypt as a string offset is an optional integer. It is the length of the prefix used by lock() if any. It defaults to 0. Return the decrypted text as a string or nil if the MAC verification fails. Note: the responsibility of using matching prefix and offset belongs to the application. --- Curve25519-based key exchange public_key(sk) => pk return the public key associated to a curve25519 secret key sk is the secret key as a 32-byte string pk is the associated public key as a 32-byte string keypair() => pk, sk generates a pair of curve25519 keys (public key, secret key) pk is the public key as a 32-byte string sk is the secret key as a 32-byte string Note: This is a convenience function: pk, sk = keypair() --is equivalent to sk = randombytes(32); pk = public_key(sk) key_exchange(sk, pk) => k DH key exchange. Return a session key k used to encrypt or decrypt a text. sk is the secret key of the party invoking the function ("our secret key"). pk is the public key of the other party ("their public key"). sk, pk and k are 32-byte strings --- Blake2b cryptographic hash blake2b_init([digest_size [, key]]) => ctx initialize and return a blake2b context object digest_size is the optional length of the expected digest. If provided, it must be an integer between 1 and 64. It defaults to 64. key is an optional key allowing to use blake2b as a MAC function. If provided, key is a string with a length that must be between 1 and 64. The default is no key. ctx is a pointer to the blake2b context as a light userdata. blake2b_update(ctx, text_fragment) update the hash with a new text fragment ctx is a pointer to a blake2b context as a light userdata. blake2b_final(ctx) => digest return the final value of the hash ctx is a pointer to a blake2b context as a light userdata. The digest is returned as a string. The length of the digest has been defined at the context creation (see blake2b_init()). It defaults to 64. blake2b(text) => digest compute the hash of a string. Returns a 64-byte digest. This is a convenience function which combines the init(), update() and final() functions above. --- Ed25519 signature sign_public_key(sk) => pk return the public key associated to a secret key sk is the secret key as a 32-byte string pk is the associated public key as a 32-byte string sign_keypair() => pk, sk generates a pair of ed25519 signature keys (public key, secret key) pk is the public signature key as a 32-byte string sk is the secret signature key as a 32-byte string Note: This is a convenience function: pk, sk = sign_keypair() --is equivalent to sk = randombytes(32); pk = sign_public_key(sk) sign(sk, text) => sig sign a text with a secret key sk is the secret key as a 32-byte string text is the text to sign as a string Return the text signature as a 64-byte string. check(sig, pk, text) => is_valid check a text signature with a public key sig is the signature to verify, as a 64-byte string pk is the public key as a 32-byte string text is the signed text Return a boolean indicating if the signature is valid or not. Note: curve25519 key pairs (generated with keypair()) cannot be used for ed25519 signature. The signature key pairs must be generated with sign_keypair(). --- Argon2i password derivation argon2i(pw, salt, nkb, niter) => k compute a key given a password and some salt This is a password key derivation function similar to scrypt. It is intended to make derivation expensive in both CPU and memory. pw: the password string salt: some entropy as a string (typically 16 bytes) nkb: number of kilobytes used in RAM (as large as possible) niter: number of iterations (as large as possible, >= 10) Return k, a key string (32 bytes). For example: on a CPU i5 M430 @ 2.27 GHz laptop, with nkb=100000 (100MB) and niter=10, the derivation takes ~ 1.8 sec Note: this implementation has no threading support, so no parallel execution.
Adjust the Makefile according to your Lua installation.
make -- build luanacha.so make test -- build luanacha.so if needed, then run test/test_luanacha.lua make clean make LUA=/path/to/lua LUAINC=/path/to/lua_include_dir test
Yes, a rockspec is due :-)
The original Monocypher source code is licensed under the following terms (from the monocypher README file):
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The LuaNacha wrapper library is MIT-licensed.