Wt::Auth::HashFunction Class Reference

An abstract cryptographic hash function interface. More...

#include <Wt/Auth/HashFunction.h>

Inheritance diagram for Wt::Auth::HashFunction:

Public Member Functions
virtual	~HashFunction ()
	Destructor.
virtual std::string	name () const =0
	Returns the name for this hash function. More...
virtual std::string	compute (const std::string &msg, const std::string &salt) const =0
	Computes the hash of a message + salt. More...
virtual bool	verify (const std::string &msg, const std::string &salt, const std::string &hash) const
	Verifies a message with the salted hash. More...

Detailed Description

An abstract cryptographic hash function interface.

A cryptographic hash function computes a hash value from a message, for which it is hard to guess another message that generates the same hash.

These hash functions are intended for short messages, typically passwords or random tokens, and thus not suitable for computing the hash value of a large document.

When used for passwords, to avoid dictionary attacks, the hash functions accept also a random salt which is hashed together with the password. Not all hash functions are adequate for passwords hashes.

Member Function Documentation

compute()

virtual std::string Wt::Auth::HashFunction::compute ( const std::string &  msg, const std::string &  salt  ) const

pure virtual

Computes the hash of a message + salt.

The message is usually an ASCII or UTF-8 string.

The salt and the computed hash are encoded in printable characters. This is usually ASCII-encoded (as for the UNIX crypt() functions) or could be Base64-encoded.

Implemented in Wt::Auth::BCryptHashFunction, Wt::Auth::SHA1HashFunction, and Wt::Auth::MD5HashFunction.

name()

virtual std::string Wt::Auth::HashFunction::name ( ) const

pure virtual

Returns the name for this hash function.

This should return a (short) name that uniquely identifies this hash function.

Implemented in Wt::Auth::BCryptHashFunction, Wt::Auth::SHA1HashFunction, and Wt::Auth::MD5HashFunction.

verify()

bool Wt::Auth::HashFunction::verify ( const std::string &  msg, const std::string &  salt, const std::string &  hash  ) const

virtual

Verifies a message with the salted hash.

The base implementation will recompute the hash of the message with the given salt, and compare it to the hash.

Some methods however store the salt and additional settings in the hash, and this information is thus needed to verify the message hash.

Reimplemented in Wt::Auth::BCryptHashFunction.