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Diffstat (limited to 'libhashsum_init_shake256_hasher.3')
| -rw-r--r-- | libhashsum_init_shake256_hasher.3 | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/libhashsum_init_shake256_hasher.3 b/libhashsum_init_shake256_hasher.3 new file mode 100644 index 0000000..d9f407e --- /dev/null +++ b/libhashsum_init_shake256_hasher.3 @@ -0,0 +1,217 @@ +.TH LIBHASHSUM_INIT_SHAKE256_HASHER 3 libhashsum +.SH NAME +libhashsum_init_shake256_hasher - initialise state for SHAKE256 hashing + +.SH SYNOPSIS +.nf +#include <libhashsum.h> + +\fBstruct libhashsum_hasher\fP { + enum libhashsum_algorithm \fIalgorithm\fP; + const char *\fIalgorithm_string\fP; + size_t \fIinput_block_size\fP; + size_t \fIhash_size\fP; + unsigned char *\fIhash_output\fP; + unsigned char \fIsupports_non_whole_bytes\fP; + size_t (*\fIprocess\fP)(struct libhashsum_hasher *\fPthis\fP, const void *\fPdata\fP, size_t \fPbytes\fP); + int (*\fIfinalise_const\fP)(struct libhashsum_hasher *\fPthis\fP, const void *\fPdata\fP, size_t \fPbytes\fP, unsigned \fPextra_bits\fP); + int (*\fIfinalise\fP)(struct libhashsum_hasher *\fPthis\fP, void *\fPdata\fP, size_t \fPbytes\fP, unsigned \fPextra_bits\fP, size_t \fPsize\fP); + void (*\fIdestroy\fP)(struct libhashsum_hasher *\fPthis\fP); + union libhashsum_state { /* definition omitted */ } \fIstate\fP; +}; + +int \fBlibhashsum_init_shake256_hasher\fP(struct libhashsum_hasher *\fIhasher\fP, size_t \fIhashbits\fP); +.fi +.PP +Link with +.I -lhashsum +.IR "-lkeccak" . + +.SH DESCRIPTION +The +.B libhashsum_init_shake256_hasher +function initialises +.I *hasher +for hashing using the cryptographic hash function +SHAKE256 (a version of SHAKE), and stores hash +function information and hashing functions for +SHAKE256 in +.IR *hasher . +.PP +.I hashbits +shall the hash size in bits or 0, for the default +hash size (256 bits). +.PP +.I hasher->algorithm +will be set to +.IR LIBHASHSUM_SHAKE256 . +.PP +.I hasher->algorithm_string +will be set to +.RB \(dq SHAKE256 \(dq, +or (if +.I hashbits +is neither 0 nor 256) +.RB \(dq SHAKE256[n= \fIhashbits\fP ] \(dq, +in which case +.I hasher->algorithm_string +will point to a buffer in +.IR hasher->state . +.PP +.I hasher->input_block_size +will be set to the block size SHAKE256 uses, in bytes. +.PP +.I hasher->hash_size +will be set to the size of SHAKE256 hashes, in bytes +.RI ( LIBHASHSUM_SHAKE256_HASH_SIZE +if +.I hashbits +is 0 or 256). +.PP +.I hasher->hash_output +will be set to +.IR NULL . +.PP +.I hasher->supports_non_whole_bytes +will be set to 1 +to indicate that the +.I *hasher->finalise +and +.I *hasher->finalise_const +functions support non-zero values in their +.I extra_bits +parameter. +.PP +.I hasher->process +will be set to a pointer to the function to call +to feed, and process, data into the hash function. +Its parameter +.I this +shall be set to +.IR hasher . +Its parameter +.I data +parameter shall be set to the buffer of data to +process, and its parameter +.I bytes +shall set to the number of bytes to process from +.IR data . +.I *hasher->process +will return the number of bytes processed, which +will be a multiple of +.IR hasher->input_block_size +no greater than +.IR bytes . +.PP +.I hasher->finalise_const +will be set to a pointer to the function to call +once the entire text being hashed has been loaded, +and to get the hash of the text. It's parameter +.I this +shall be set to +.IR hasher . +Its parameter +.I data +shall be set to the beginning of any yet unprocessed +data, and its parameter +.I bytes +shall be set to the number of bytes to process from +.IR data . +Its parameter +.I extra_bits +shall be set to the number of bits to process from +the lower bits of the incomplete byte +.IR data[bytes] . +The +.I *hasher->finalise_const +function will return 0 upon successful completion, +and set +.I hasher->hash_output +to a pointer to a buffer in +.I hasher->state +containing the binary hash of the processed data. +Otherwise, the function will return -1, and set +.I errno +to indicate the error. The function will failure +if: +.RS +.TP +.B EINVAL +.I extra_bits +is 8 or greater. +.RE +.PP +.I hasher->finalise +will be set to the pointer to a function that +is an alternative to +.I *hasher->finalise_const +that can support zero-copy provided that the +buffer input as the argument +.I data +is sufficiently large. The +.I *hasher->finalise +function may rewrite +.I data +and shall is does not safe to use for multiple +hashers (if the same text is hashed using multiple +hashers, +.I *hasher->finalise_const +must be used). The +function's parameter +.I size +shall be set to the size of the buffer +.IR data . +.I *hasher->finalise +is otherwise identical to +.IR *hasher->finalise_const . +.PP +.I hasher->destroy +will be set to a pointer to a function to to +call, with +.I hasher +as the argument, deallocate dynamically +allocated data, which may invalidate any +pointer in +.IR *hasher . +.PP +.I hasher->state +will be initialised, it shall be treated as +internal to the library's implementation, and +may change between versions. +.PP +.I hasher +must not be +.IR NULL . + +.SH RETURN VALUE +Upon successful completion, the +.B libhashsum_init_shake256_hasher +function returns 0. Otherwise, +the function returns -1 and sets +.I errno +to indicate the error. If -1 +is returned, the state of +.I *hasher +is undefined. + +.SH ERRORS +The +.B libhashsum_init_shake256_hasher +function fails if: +.TP +.B ENOSYS +Support was excluded at compile time. +.TP +.B ENOMEM +Insufficient memory available. +.TP +.B EINVAL +.I hashbits +is too large. + +.SH HISTORY +libhashsum 1.0. + +.SH SEE ALSO +.BR libhashsum (7), +.BR libhashsum_init_shake_hasher (3) |