mhash
mhash(3) mhash library mhash(3)
NAME
mhash - Hash Library
VERSION
mhash 0.8.16
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 vari-
ants 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 func-
tions 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 partic-
ular 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 sup-
ported. 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 mal-
loc(3) seperately, 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 leak-
ing 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. KEY-
GEN_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 key-
word 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 algo-
rithm_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_key-
gen_count()".
char *mhash_get_keygen_name(keygenid type);
If type exists, this returns the name of the keygen type. Other-
wise, a "NULL" pointer is returned. The string is allocated with
malloc(3) seperately, 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. Other-
wise, 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 (preferrably together with a
patch) to the maintainer with a detailed description on how to repro-
duce the bug.
AUTHORS
Sascha Schumann <sascha@schumann.cx> Nikos Mavroyanopoulos <nmav@hel-
lug.gr>
3rd Berkeley Distribution 2000/03/23 mhash(3)
