mhash(3)

NAME
mhash - Hash Library

VERSION
mhash .9.2

SYNOPSIS
 #include "mhash.h"

Informative Functions

 size_t   mhash_count(void);
 size_t   mhash_get_block_size(hashid type);
 char    *mhash_get_hash_name(hashid type);
 size_t   mhash_get_hash_pblock(hashid type);
 hashid   mhash_get_mhash_algo( MHASH);

Key Generation Functions

 int      mhash_keygen_ext(keygenid algorithm, KEYGEN algorithm_data,
                void* keyword, int keysize,
                unsigned char* password, int passwordlen);

Initializing Functions

 MHASH    mhash_init(hashid type);
 MHASH    mhash_hmac_init(const hashid type, void *key, int keysize, int block);
 MHASH    mhash_cp( MHASH);

Update Functions

 int      mhash(MHASH thread, const void *plaintext, size_t size);

Save/Restore Functions

 int      mhash_save_state_mem(MHASH thread, void *mem, int* mem_size );
 MHASH    mhash_restore_state_mem(void* mem);

Finalizing Functions

 void    mhash_deinit(MHASH thread, void *result);
 void    *mhash_end(MHASH thread);
 void    *mhash_end_m(MHASH thread, void* (*hash_malloc)(size_t));

 void    *mhash_hmac_end(MHASH thread);
 void    *mhash_hmac_end_m(MHASH thread, void* (*hash_malloc)(size_t));
 int     mhash_hmac_deinit(MHASH thread, void *result);

Available Hashes

CRC32: The crc32 algorithm is used to compute checksums. The two variants used in mhash are: MHASH_CRC32 (like the one used in ethernet) and MHASH_CRC32B (like the one used in ZIP programs).

ADLER32: The adler32 algorithm is used to compute checksums. It is faster than CRC32 and it is considered to be as reliable as CRC32. This algorithm is defined as MHASH_ADLER32.

MD5: The MD5 algorithm by Ron Rivest and RSA. In mhash this algorithm is defined as MHASH_MD5.

MD4: The MD4 algorithm by Ron Rivest and RSA. This algorithm is considered broken, so don't use it. In mhash this algorithm is defined as MHASH_MD4.

SHA1/SHA256: The SHA algorithm by US. NIST/NSA. This algorithm is specified for use in the NIST's Digital Signature Standard. In mhash these algorithm are defined as MHASH_SHA1 and MHASH_SHA256.

HAVAL: HAVAL is a one-way hashing algorithm with variable length of output. HAVAL is a modification of MD5. Defined in mhash as: MHASH_HAVAL256, MHASH_HAVAL192, MHASH_HAVAL160, MHASH_HAVAL128.

RIPEMD160: RIPEMD-160 is a 160-bit cryptographic hash function, designed by Hans Dobbertin, Antoon Bosselaers, and Bart Preneel. It is intended to be used as a secure replacement for the 128-bit hash functions MD4, MD5, and RIPEMD. MD4 and MD5 were developed by Ron Rivest for RSA Data Security, while RIPEMD was developed in the framework of the EU project RIPE (RACE Integrity Primitives Evaluation, 1988-1992). In mhash this algorithm is defined as MHASH_RIPEMD160.

TIGER: Tiger is a fast hash function, by Eli Biham and Ross Anderson. Tiger was designed to be very fast on modern computers, and in particular on the state-of-the-art 64-bit computers, while it is still not slower than other suggested hash functions on 32-bit machines. In mhash this algorithm is defined as: MHASH_TIGER, MHASH_TIGER160, MHASH_TIGER128.

GOST: GOST algorithm is a russian standard and it uses the GOST encryption algorithm to produce a 256 bit hash value. This algorithm is specified for use in the Russian Digital Signature Standard. In mhash this algorithm is defined as MHASH_GOST.

Available Key Generation algorithms

KEYGEN_MCRYPT: The key generator used in mcrypt.

KEYGEN_ASIS: Just returns the password as binary key.

KEYGEN_HEX: Just converts a hex key into a binary one.

KEYGEN_PKDES: The transformation used in Phil Karn's DES encryption program.

KEYGEN_S2K_SIMPLE: The OpenPGP (rfc2440) Simple S2K.

KEYGEN_S2K_SALTED: The OpenPGP Salted S2K.

KEYGEN_S2K_ISALTED: The OpenPGP Iterated Salted S2K.

DESCRIPTION
The mhash library provides an easy to use C interface for several hash algorithms (also known as "one-way" algorithms). These can be used to create checksums, message digests and more. Currently, MD5, SHA1, GOST, TIGER, RIPE-MD160, HAVAL and several other algorithms are supported. mhash support HMAC generation (a mechanism for message authentication using cryptographic hash functions, and is described in rfc2104). HMAC can be used to create message digests using a secret key, so that these message digests cannot be regenerated (or replaced) by someone else. A key generation mechanism was added to mhash since key generation algorithms usually involve hash algorithms.

API FUNCTIONS
We will describe the API of mhash in detail now. The order follows the one in the SYNOPSIS directly.

size_t mhash_count(void);
    This returns the "hashid" of the last available hash. Hashes are numbered from 0 to "mhash_count()".

size_t mhash_get_block_size(hashid type);
    If type exists, this returns the used blocksize of the hash type in bytes. Otherwise, it returns 0.

char *mhash_get_hash_name(hashid type);
    If type exists, this returns the name of the hash type. Otherwise, a "NULL" pointer is returned. The string is allocated with malloc(3) separately, so do not forget to free(3) it.

const char *mhash_get_hash_name_static(hashid type);
    If type exists, this returns the name of the hash type. Otherwise, a "NULL" pointer is returned.

size_t mhash_get_hash_pblock(hashid type);
    It returns the block size that the algorithm operates. This is used in mhash_hmac_init. If the return value is 0 you shouldn't use that algorithm in HMAC.

hashid mhash_get_mhash_algo(MHASH src);
    Returns the algorithm used in the state of src.

MHASH mhash_init(hashid type);
    This setups a context to begin hashing using the algorithm type. It returns a descriptor to that context which will result in leaking memory, if you do not call mhash_deinit(3) later. Returns "MHASH_FAILED" on failure.

MHASH mhash_hmac_init(const hashid type, void *key, int keysize, int block);
    This setups a context to begin hashing using the algorithm type in HMAC mode. key should be a pointer to the key and keysize its len. The block is the block size (in bytes) that the algorithm operates. It should be obtained by mhash_get_hash_pblock(). If its 0 it defaults to 64. After calling it you should use mhash() to update the context. It returns a descriptor to that context which will result in leaking memory, if you do not call mhash_hmac_deinit(3) later. Returns "MHASH_FAILED" on failure.

MHASH mhash_cp(MHASH src);
    This setups a new context using the state of src.

int mhash(MHASH thread, const void *plaintext, size_t size);
    This updates the context described by thread with plaintext. size is the length of plaintext which may be binary data.

int mhash_save_state_mem( MHASH thread, void *mem, int* mem_size);
    Saves the state of a hashing algorithm such that it can be restored at some later point in time using mhash_restore_state_mem(). mem_size should contain the size of the given mem pointer. If it is not enough to hold the buffer the required value will be copied there.

MHASH mhash_restore_state_mem(void* mem);
    Restores the state of a hashing algorithm that was saved using mhash_save_state_mem(). Use like mhash_init().

void *mhash_end(MHASH thread);
    This frees all resources associated with thread and returns the result of the whole hashing operation (the ``digest'').

void mhash_deinit(MHASH thread, void* digest);
    This frees all resources associated with thread and stores the result of the whole hashing operation in memory pointed by digest. digest may be null.

void *mhash_hmac_end(MHASH thread);
    This frees all resources associated with thread and returns the result of the whole hashing operation (the ``mac'').

int mhash_hmac_deinit(MHASH thread, void* digest);
    This frees all resources associated with thread and stores the result of the whole hashing operation in memory pointed by digest. Digest may be null. Returns non-zero in case of an error.

void *mhash_end_m(MHASH thread, void* (*hash_malloc)(size_t));
    This frees all resources associated with thread and returns the result of the whole hashing operation (the ``digest''). The result will be allocated by using the hash_malloc() function provided.

void *mhash_hmac_end(MHASH thread, void* (*hash_malloc)(size_t));
    This frees all resources associated with thread and returns the result of the whole hashing operation (the ``mac''). The result will be allocated by using the hash_malloc() function provided.

KEYGEN API FUNCTIONS
We will now describe the Key Generation API of mhash in detail.

int mhash_keygen_ext(keygenid algorithm, KEYGEN algorithm_data, void* keyword, int keysize, unsigned char* password, int passwordlen);
    This function, generates a key from a password. The password is read from password and it's len should be in passwordlen. The key generation algorithm is specified in algorithm, and that algorithm may (internally) use the KEYGEN structure. The KEYGEN structure consists of:
     typedef struct keygen {
            hashid hash_algorithm[2];
            unsigned int count;
            void* salt;
            int salt_size;
     } KEYGEN;

    The algorithm(s) specified in algorithm_data.hash_algorithm, should be hash algorithms and may be used by the key generation algorithm. Some key generation algorithms may use more than one hash algorithms (view also mhash_keygen_uses_hash_algorithm()). If it is desirable (and supported by the algorithm, eg. KEYGEN_S2K_SALTED) a salt may be specified in algorithm_data.salt of size algorithm_data.salt_size or may be NULL.

    The algorithm may use the algorithm_data.count internally (eg. KEYGEN_S2K_ISALTED). The generated keyword is stored in keyword, which should be (at least) keysize bytes long. The generated keyword is a binary one. Returns a negative number on failure.

int mhash_keygen_uses_salt( keygenid algorithm);
    This function returns 1 if the specified key generation algorithm needs a salt to be specified.

int mhash_keygen_uses_count( keygenid algorithm);
    This function returns 1 if the specified key generation algorithm needs the algorithm_data.count field in mhash_keygen_ext(). The count field tells the algorithm to hash repeatedly the password and to stop when count bytes have been processed.

int mhash_get_keygen_salt_size( keygenid algorithm);
    This function returns the size of the salt size, that the specific algorithm will use. If it returns 0, then there is no limitation in the size.

int mhash_get_keygen_max_key_size( keygenid algorithm);
    This function returns the maximum size of the key, that the key generation algorithm may produce. If it returns 0, then there is no limitation in the size.

int mhash_keygen_uses_hash_algorithm( keygenid algorithm);
    This function returns the number of the hash algorithms the key generation algorithm will use. If it is 0 then no hash algorithm is used by the key generation algorithm. This is for the algorithm_data.hash_algorithm field in mhash_keygen_ext(). If

size_t mhash_keygen_count(void);
    This returns the "keygenid" of the last available key generation algorithm. Algorithms are numbered from 0 to "mhash_keygen_count()".

char *mhash_get_keygen_name(keygenid type);
    If type exists, this returns the name of the keygen type. Otherwise, a "NULL" pointer is returned. The string is allocated with malloc(3) separately, so do not forget to free(3) it.

const char *mhash_get_keygen_name_static(keygenid type);
    If type exists, this returns the name of the keygen type. Otherwise, a "NULL" pointer is returned.

EXAMPLE
Hashing STDIN until EOF.

 #include <mhash.h>
 #include <stdio.h>
 #include <stdlib.h>

 int main(void)
 {
        int i;
        MHASH td;
        unsigned char buffer;
        unsigned char hash[16]; /* enough size for MD5 */

        td = mhash_init(MHASH_MD5);

        if (td == MHASH_FAILED) exit(1);

        while (fread(&buffer, 1, 1, stdin) == 1) {
                mhash(td, &buffer, 1);
        }

        mhash_deinit(td, hash);

        printf("Hash:");
        for (i = 0; i < mhash_get_block_size(MHASH_MD5); i++) {
                printf("%.2x", hash[i]);
        }
        printf("\n");

        exit(0);
 }

EXAMPLE
An example program using HMAC:

 #include <mhash.h>
 #include <stdio.h>

 int main()
 {

        char password[] = "Jefe";
        int keylen = 4;
        char data[] = "what do ya want for nothing?";
        int datalen = 28;
        MHASH td;
        unsigned char mac[16];
        int j;

        td = mhash_hmac_init(MHASH_MD5, password, keylen,
                            mhash_get_hash_pblock(MHASH_MD5));

        mhash(td, data, datalen);
        mhash_hmac_deinit(td, mac);

 /*
  * The output should be 0x750c783e6ab0b503eaa86e310a5db738
  * according to RFC 2104.
  */

        printf("0x");
        for (j = 0; j < mhash_get_block_size(MHASH_MD5); j++) {
                printf("%.2x", mac[j]);
        }
        printf("\n");

        exit(0);
 }

HISTORY
This library was originally written by Nikos Mavroyanopoulos <nmav@hellug.gr> who passed the project over to Sascha Schumann <sascha@schumann.cx> in May 1999. Sascha maintained it until March 2000. The library is now maintained by Nikos Mavroyanopoulos.

BUGS
If you find any, please send a bug report (preferably together with a patch) to the maintainer with a detailed description on how to reproduce the bug.

AUTHORS
Sascha Schumann <sascha@schumann.cx> Nikos Mavroyanopoulos <nmav@hellug.gr>