# crypto Module

The crypto modules provides various functions for working with cryptographic algorithms.

## crypto.hash()

Compute a cryptographic hash of a Lua string.

####Syntax
`hash = crypto.hash(algo, str)`

####Parameters
  - `algo`: The hash algorithm to use, case insensitive string

Supported hash algorithms are:
  - MD2 (not available by default, has to be explicitly enabled in user_config.h)
  - MD5
  - SHA1
  - SHA256, SHA384, SHA512 (unless disabled in user_config.h)

####Returns
A binary string containing the message digest. To obtain the textual version (ASCII hex characters), please use `crypto.toHex()`.

####Example
```lua
print(crypto.toHex(crypto.hash("sha1","abc")))
```
___
## crypto.hmac()

Compute a HMAC (Hashed Message Authentication Code) signature for a Lua string.

## Syntax
`signature = crypto.hmac(algo, str, key)`

####Parameters
  - algo: hash algorithm to use, case insensitive string
  - str: data to calculate the hash for
  - key: key to use for signing, may be a binary string

Supported hash algorithms are:
  - MD2 (not available by default, has to be explicitly enabled in user_config.h)
  - MD5
  - SHA1
  - SHA256, SHA384, SHA512 (unless disabled in user_config.h)

####Returns
A binary string containing the HMAC signature. Use `crypto.toHex()` to obtain the textual version.

####Example
```lua
print(crypto.toHex(crypto.hmac("sha1","abc","mysecret")))
```
___
## crypto.mask()

Applies an XOR mask to a Lua string. Note that this is not a proper cryptographic mechanism, but some protocols may use it nevertheless.

####Syntax
masked = crypto.mask (message, mask)

####Parameters
  - message: message to mask
  - mask = the mask to apply, repeated if shorter than the message

####Returns
The masked message, as a binary string. Use `crypto.toHex()` to get a textual representation of it.

####Example
```lua
print(crypto.toHex(crypto.mask("some message to obscure","X0Y7")))
```
___
## crypto.toHex()

Provides an ASCII hex representation of a (binary) Lua string. Each byte in the input string is represented as two hex characters in the output.

####Syntax
`hexstr = crypto.toHex(binary)`

####Parameters
  - `binary`: input string to get hex representation for

####Returns
An ASCII hex string.

####Example
```lua
print(crypto.toHex(crypto.hash("sha1","abc")))
```
___
## crypto.toBase64()

Provides a Base64 representation of a (binary) Lua string.

####Syntax
`b64 = crypto.toBase64(binary)`

####Parameters
  - `binary`: input string to Base64 encode

####Return
A Base64 encoded string.

####Example
```lua
print(crypto.toBase64(crypto.hash("sha1","abc")))
```
___