.TH LIBHASHSUM_INIT_KECCAK_HASHER 3 libhashsum .SH NAME libhashsum_init_keccak_hasher - initialise state for Keccak hashing .SH SYNOPSIS .nf #include \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; unsigned char \fIstandard_partial_byte_input_encoding\fP; unsigned char \fIstandard_partial_byte_output_encoding\fP; unsigned char \fIhash_excess_bits\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 (*\fIstretch\fP)(struct libhashsum_hasher *\fPthis\fP, int \fPskip\fP, void *\fPbuffer\fP); void (*\fIdestroy\fP)(struct libhashsum_hasher *\fPthis\fP); union libhashsum_state { /* definition omitted */ } \fIstate\fP; }; int \fBlibhashsum_init_keccak_hasher\fP(struct libhashsum_hasher *\fIhasher\fP, size_t \fIratebits\fP, size_t \fIcapbits\fP, size_t \fIhashbits\fP, size_t \fIsqueezes\fP); .fi .PP Link with .I -lhashsum .IR "-lkeccak" . .SH DESCRIPTION The .B libhashsum_init_keccak_hasher function initialises .I *hasher for hashing using the cryptographic hash function Keccak, and stores hash function information and hashing functions for Keccak in .IR *hasher . .PP .I ratebit shall be the rate, in bits per \(dqabsorption\(dq, of the hash function, or 0 if it shall be resolved to an automatically determined value. .PP .I capbits shall be the capacity, in bits, of the hash function's \(dqsponge\(dq, or 0 if it shall be resolved to an automatically determined value. .PP .I hashbits shall be the hash size, in bits or 0 if it shall be resolved to an automatically determined value. .PP .I squeezes shall be the number of \(dqsponge squeezes\(dq to perform at the end phase when producing the hash, or 0 if it shall be resolved to an automatically determined value (which will always be 1). .PP .I hasher->algorithm will be set to .I LIBHASHSUM_KECCAK_224 (if .I (ratebits, capbits, hashbits, squeezes) have the values (1152, 448, 224, 1) after zeroes have been resolved), .I LIBHASHSUM_KECCAK_256 (if .I (ratebits, capbits, hashbits, squeezes) have the values (1088, 512, 256, 1) after zeroes have been resolved), .I LIBHASHSUM_KECCAK_384 (if .I (ratebits, capbits, hashbits, squeezes) have the values (832, 768, 384, 1) after zeroes have been resolved), .I LIBHASHSUM_KECCAK_512 (if .I (ratebits, capbits, hashbits, squeezes) have the values (576, 1024, 512, 1) after zeroes have been resolved), or .I LIBHASHSUM_KECCAK (otherwise). .PP .I hasher->algorithm_string will be set to .RB \(dq Keccak-224 \(dq if .I hasher->algorithm was set to .IR LIBHASHSUM_KECCAK_224 , .RB \(dq Keccak-256 \(dq if .I hasher->algorithm was set to .IR LIBHASHSUM_KECCAK_256 , .RB \(dq Keccak-384 \(dq if .I hasher->algorithm was set to .IR LIBHASHSUM_KECCAK_384 , .RB \(dq Keccak-512 \(dq if .I hasher->algorithm was set to .IR LIBHASHSUM_KECCAK_512 , and otherwise to .RB \(dq Keccak[r= \fIratebits\fP ,c= \fIcapbits\fP ,n= \fIhashbits\fP ] \(dq if .I squeezes<2 or .RB \(dq Keccak[r= \fIratebits\fP ,c= \fIcapbits\fP ,n= \fIhashbits\fP z= \fIsqueezes\fP ] \(dq (if .IR squeezes>1 ), where .IR ratebits , .IR capbits , and .I hashbits have their resolved non-zero values. For the later two cases, .I hasher->algorithm_string will be a pointer to a buffer in .IR hasher->state . .PP .I hasher->input_block_size will be set to the block size, in bytes .RI ( ratebits/8 unless .IR ratebits==0 ). .PP .I hasher->hash_size will be set to the hash size, in bytes .RI ( (hashbits+7)/8 unless .IR hashbits==0 ). .PP .I hasher->hash_excess_bits will be set to number of bits the last byte in the hash is padded with (it will be padded with cleared bits in its most significant part). As long as .I hashbits is a multiple of 8, this number will be 0 (the entire last byte is used), otherwise, it will be .IR 8-(hashbits&7) . .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. Its 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. However, if the user has already set .I hasher->hash_output to a .RI non- NULL pointer, the function will output the binary hash to that pointer instead without redirecting .I hasher->hash_output (the application must make sure this buffer is sufficiently large). 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->stretch will be set to .IR NULL , however upon successful completion of .I *hasher->finalise or .IR *hasher->finalise_const , .I hasher->stretch will be set to point to a function that can be used to extend the hash by .I hasher->hash_size bytes, and can be called repeated without limitation. The hash extent will be written to a buffer in .I hasher->state (which .I *hasher->finalize and .I *hasher->finalize_const also write the hash to), and .I hasher->hash_output will be set to point to this buffer. .IR *hasher->stretch 's parameter .I this shall be .IR hasher . Its parameter .I skip can be set to non-zero if the hash extent should be discarded .RI ( hasher->hash_output will not be set in this case). Its parameter .I buffer shall be .I NULL for the above described behaviour, or an sufficiently large buffer the function shall output the hash extent to. If .I buffer is .RI non- NULL , .I hasher->hash_output will be set to .IR NULL ). .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_keccak_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_keccak_hasher function fails if: .TP .B ENOSYS Support was excluded at compile time. .TP .B ENOMEM Insufficient memory available. .TP .B EINVAL The combination of the values .IR ratebits , .IR capbits , and .I hashbits is invalid (possibly any single value is invalid). .SH EXTENDED DESCRIPTION libhashsum has normalises the all implemented hash functions to always use the least significant bits in non-whole octets, however each hash function has its unstandarded. To make it easier to create an application the use the same encoding of partial octets as other application using any particular hash function, .B struct libhashsum_hasher contains two fields: .I standard_partial_byte_input_encoding and .IR standard_partial_byte_output_encoding ; which are merely informtional. They are not set to specify how libhashsum expects and encodes non-whole octets, but rather specify how partial bytes are encoded in the reference implementation or specification of a hash function. .PP Keccak supports non-whole octet both in its input and its output, and in its standard uses the least significant bits of non-whole octets both in the input and in the output, thus .I this->standard_partial_byte_input_encoding and .I this->standard_partial_byte_output_encoding will both be set to .IR LIBHASHSUM_LEAST_SIGNIFICANT , which the same behaviour as libhashsum implements. .SH HISTORY Introduced in libhashsum 1.0. .PP The .I hash_excess_bits field was added in libhashsum 1.1. .SH SEE ALSO .BR libhashsum (7), .BR libhashsum_init_keccak_224_hasher (3), .BR libhashsum_init_keccak_256_hasher (3), .BR libhashsum_init_keccak_384_hasher (3), .BR libhashsum_init_keccak_512_hasher (3)