Convert Lua file to C file with all functions encrypted
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README.md

luacryptor

Convert Lua file to C file with all functions encrypted

To get list of commands, run luacryptor.lua without arguments.

Luacryptor creates .c file, which can be compiled into binary library. Loading this library into Lua works as if original Lua module was loaded.

Loading requires password. Set password in Lua registry.

Lua:

    debug.getregistry().__luacryptor_pwd = "password"

C:

    lua_pushstring(L, "password");
    lua_setfield(L, LUA_REGISTRYINDEX, "__luacryptor_pwd");

Command embed encrypts whole Lua file. No restrictions on source Lua file.

Command encfunc encrypts individual functions in Lua module. Lua module must return table, all elements of which are functions. Functions may have up to one upvalue, module itself. Source of luacryptor.lua can serve as example.

Option --bytecode tells luacryptor to compile Lua sources to bytecode before encrypting. Target and Host Lua version must have compatible bytecode versions.

Installation

Using LuaRocks:

$ sudo luarocks install luacryptor

Encryption

Twofish with 256 bit key in CTR mode. CTR mode is implemented as follows:

  • 16 bytes (nonce) are read from /dev/urandom and written in the beginning of cryptotext.
  • int counter = 0
  • For each block:
    • Calculate XOR(nonce, counter). Counter is aligned to the end of block in Big-endian mode.
    • Twofish(block)
    • XOR result with input
    • Increment counter

No padding required. CTR works like stream mode.

Password is hashed with SHA-256. Function names are replaced with sha256(password .. name).

File and function bodies are encrypted with twofish with key=sha256(password .. name).