Introduction
MD5 offers basic cryptographic facilities for Lua 5.1: a hash (digest) function, and a pair crypt/decrypt.
MD5 is free software and uses the same license as Lua.
Building
MD5 offers a Makefile and a separate configuration file, config
,
which should be edited to suit the particularities of the target platform
before running make
.
The file has some definitions like paths to the external libraries,
compiler options and the like. One important definition is the Lua version,
which is not obtained from the installed software.
Installation
The compiled binary file should be copied to a directory called md5
in your
C path
with the name core.[so|dll]
. Windows users can use the binary version
of MD5 available at
LuaForge.
The file md5.lua
should be copied to a directory in your
Lua path.
Reference
Lua API
All MD5 functions are registered inside a table md5
.
- md5.sum (message)
- Computes the MD5 message-digest of the string
message
. This function takes as input a message of arbitrary length and content and returns as output a 128-bit "fingerprint" (or "message digest") of the input.
The output is formated as a binary string with 16 characters. It is conjectured that it is computationally infeasible to produce two messages having the same message digest, or to produce any message having a given pre-specified target message digest. (see RFC 1321) - md5.sumhexa (message)
- Similar to
md5.sum
, but returns its value as a string of 32 hexadecimal digits. - md5.crypt (message, key [,seed])
- Encrypts a string, using MD5 in CFB (Cipher-feedback mode).
message
is an arbitrary binary string to be encrypted.key
is an arbitrary binary string to be used as a key.seed
is an arbitrary binary string to be used as a seed; Returns the cyphertext (as a binary string).
If no seed is provided, the function uses the result ofos.time()
as a seed. It is recommended that you use different seeds for each message; the seed itself is not private, and should contain no private data, because it goes plain in the beginning of the encrypted message.
The length of the cyphertext is the length of the message plus the length of the seed plus one. - md5.decrypt (message, key)
- Decrypts a string. The input
message
must be the result of a previous call tocrypt
. For anymsg
,key
, andseed
, we have thatmd5.decrypt(md5.crypt(msg, key, seed), key) == msg
- md5.exor (s1, s2)
- Does a bit-a-bit exclusive or of strings
s1
ands2
. Both strings must have the same length, which will be also the length of the resulting string.
C API
The following functions are declared in md5.h
- int luaopen_md5_core (lua_State *L)
- Opens the library and registers the above Lua functions in the given state.
- void md5 (const char *message, long len, char *output)
- Computes the MD5 message-digest of
message
.len
is the length ofmessage
.output
is a buffer that receives the result; it must have at least 16 bytes (128 bits).