HomeSYNOPSIS
success = hash:init(alg)
DESCRIPTION
The Core4 system includes a copy of mbed TLS.
This function (re-)initializes an object for calculating one-way hashes (message digests).
The parameter alg names the desired message digest algorithm.
Supported algorithms are: MD2, MD4, MD5, SHA1, SHA224, SHA256, SHA384, SHA512, RIPEMD160.
After initialization, data is fed to the algorithme by calling hash:update().
The result can be retrieved by calling hash:finish().
RETURN VALUE
On success, returns true.
If initialization failed, returns nil, a string describing the error and the mbedtls error code number.