libkhash/README.org

• libkhash - kana-hash
  • Example output
  • Installation
    • Build and install
    • Uninstall
    • Other build configurations
      • Native code optimisations
      • Tests
      • Building the CLI
  • Rust crate
  • C header
    • Example
    • Definitions
      • Macros
      • Types
      • Functions
  • Node FFI bindings
    • Installation (npm)
    • Examples
      • Import the package
      • Create a context
      • Create a hash
        • Creating a hash without consuming
        • Freeing the context
        • Cloning an existing context
      • Alternatively
    • Interface documentation
      • Defined constants
  • Notes
    • Digest algorithm
  • License

libkhash - kana-hash

Kana mnemonic hashes

Example output

Input is uguu~ using the default salt.

Algorithm	Output
SHA256	おシソまツアでぅせツモァだゅノびヲろぢォセつマぶけぁユねハァがゅ
CRC32	わぼぢァ
CRC64	づやワえぼちレこ
SHA256 (truncated)	おシソまツアで

Installation

The dynamic library is built with Cargo and Rust, and the cli example program is built with gcc.

Build and install

The default build configuration builds both the dynamic library and the cli example program, and copies them to /usr/lib/libkhash.so and /usr/bin/kana-hash respectively.

$ make && sudo make install

The install path can be changed by editing the INSTALL and INSTALL-BIN paths in the Makefile.

Uninstall

To remove installed binaries, run:

$ sudo make uninstall

Other build configurations

The Makefile contains some other build directives.

Native code optimisations

By default libkhash builds the shared library with native architecture optimisations enabled. If you are intending to move the binary to another architecture, this might not be desireable. To build without such optimisations, run:

$ make khash-nonative

Tests

To build and run all tests, run:

$ make test

Building the CLI

The default make directive builds both the library and the CLI example program. To build just the CLI example program, run:

$ cd cli && make

TODO Rust crate

C header

A header file is provided for C programs wanting to use the khash interface. Documented more fully in ./include/khash.h. All symbols defined here begin with either KHASH_ (for macros) or khash_.

Example

To create a context

#include <khash.h>

const char* input_salt = "salt!";
const char* input_data = "some data to hash".
khash_context ctx;
assert(khash_new_context(KHASH_ALGO_SHA256, KHASH_SALT_TYPE_SPECIFIC, input_salt, strlen(input_salt), &ctx) == KHASH_SUCCESS, "khash_new_context() failed.");

Find the buffer length we need and allocate a buffer.

size_t length;
assert(khash_length(&ctx, input_data, strlen(input_data), &length) == KHASH_SUCCESS, "khash_length() failed.");

Create the buffer and hash, then print the result to stdout.

  char* buffer = alloca(length+1);
  assert(khash_do(&ctx, input_data, strlen(input_data), buffer, length) == KHASH_SUCCESS, "khash_do() failed.");
  buffer[length] = 0; // Ensure we have a NUL terminator.

  setlocale(LC_ALL, ""); //Ensure we can print UTF-8.
  printf("Kana hash: %s\n", buffer);

Alternatively, we can allocate the max length needed instead of calculating it.

size_t length;
assert(khash_max_length(KHASH_ALGO_SHA256, strlen(input_data), &length) == KHASH_SUCCESS, "khash_max_length() failed.");
char* buffer = alloca(length+1);
memset(buffer, 0, length+1); //Ensure NUL terminators.

Definitions

Macros

All macros defined are for options. They cannot be combied as flags. The KHASH_ALGO_ prefixed ones are for use as the algo parameter in the khash_new_context() function. The KHASH_SALT_TYPE_ prefixed ones are for use as the salt_type parameter. The KHASH_ERROR_ prefixed ones each indicate an error code returned by all of the functions.

Name	Description
KHASH_ALGO_DEFAULT	The default algorithm used by the library (truncated SHA256)
KHASH_ALGO_CRC32	CRC32 checksum algorithm
KHASH_ALGO_CRC64	CRC64 checksum algorithm
KHASH_ALGO_SHA256	SHA256 hash algorithm
KHSAH_ALGO_SHA256_TRUNCATED	SHA256 truncated to 64-bits
KHASH_SALT_TYPE_NONE	No salt
KHASH_SALT_TYPE_DEFAULT	The default static salt used by the library
KHASH_SALT_TYPE_SPECIFIC	A provided salt, as the data and of the size parameter passed to khash_new_context()
KHASH_SALT_TYPE_RANDOM	A randomly generated salt
KHASH_SUCCESS	The code returned by all of the functions when the operation was successful
KHASH_ERROR_IO	There was an IO error
KHASH_ERROR_FORMAT	The was a text formatting related error
KHASH_ERROR_LENGTH	There was a hash length mismatch
KHASH_ERROR_RNG	The random number generator failed
KHASH_ERROR_UNKNOWN	There was an unknown error or the stack attempted to unwind past the FFI boundary.

Types

There are 2 exported structs, although you will rarely need to access their members directly.

Name	Field	Description
khash_salt		A salt allocated into a context by khash_new_context() and released by khash_free_context(). You shouldn't mess with its field directly.
	salt_type	The type of the salt.
	size	The size of the salt.
	body	A pointer to the body of the salt. (The memory allocated here is not guaranteed to be of the provided size.)
khash_context		A context for the khash_ functions. Allocated by khash_new_context(). You can modify its fields if you want.
	algo	The algorithm for this context.
	flags	Placeholder for potential flags added in the future. Currently unused.
	salt	The allocated salt. You shouldn't directly mess with this field.

Functions

All defined functions return either KHASH_SUCCESS or one of the KHASH_ERROR_ values above.

Name	Parameters	Description
khash_new_context	algo, salt_type, data, size, output	Creates a new context for use with other libkhash functions. algo is expected to be one of the KHASH_ALGO_ macros listed above. Likewise salt_type is expected to be one of the KHASH_SALT_TYPE_ macros. data can be NULL unless salt_type is set to KHASH_SALT_TYPE_SPECIFIC, in which exactly size bytes are read from data. output is expected to be a valid pointer to a currently unused `khash_context` structure.
khash_free_context	ctx	Free a context allocated with khash_new_context(). ctx is expected to be a valid pointer to a currently allocated context.
khash_clone_context	src, dst	Clone a context allocated with khash_new_context() into another. The newly allocated dst must be properly released (with khash_free_context() or khash_do()) as well as the source. src is expected to be a valid pointer to an allocated context, and dst is expected to be a valid pointer to an unallocated context.
khash_length	ctx, data, size, length	Compute the length required to hold the output string for khash_do() for a given input. Will read exactly size bytes from data and compute the value into what is pointed to by length (which is expected to be a valid pointer to a type of size_t.) The resulting length does not include a NUL terminator for the string.
khash_do	ctx, data, size, output, output_size	Compute the kana-hash of size bytes from data and store no more than output_size of the the result into the string pointed to by output. Each pointer is expected to be valid. This function frees the supplied ctx after the hash has been computed, and thus ctx is no longer valid afterwards.
khash_max_length	algo, input_len, output_len	Calculate the max possible size for the given algorithm (expected to be one of the KHASH_ALGO_ macros) and input length, and store this result in output_len (expected to be a valid non-NULL pointer.) input_len is not required unless the algorithm is dynamically sized (all currently implemented ones are not.)

Node FFI bindings

NPM package in ./node

Installation (npm)

Follow the /flanchan/libkhash/src/commit/4ed44555f3cc0642c3091a215d01bb82a6377cab/installation section first.

$ npm install --save /path/to/repo/node

Examples

Import the package

const hash = require('kana-hash');

Create a context

Create the context by specifying an algorithm identifier, and an optional salt. If provided, the salt must be of type Salt.

const ctx = new hash.Kana(hash.Kana.ALGO_DEFAULT, new hash.Salt("optional salt~"));

Create a hash

The once() function consumes the context and outputs a hash string.

const output = ctx.once("input string");

Creating a hash without consuming

If you want to reuse the context, use the hash() function.

const output = ctx.hash("input string");

Freeing the context

The context must be release after use if you have not called once().

ctx.finish();

Cloning an existing context

The new context must also be freed with either once() or finish().

const new_ctx = ctx.clone();

Alternatively

To create a hash in one line you can do one of the following.

  const hash1 = new Kana(Kana.ALGO_DEFAULT, new Salt("salt~")).once("input string~"); //Allocates the exact space required for the output string.
  const hash2 = Kana.single(Kana.ALGO_DEFAULT, new Salt("salt~")).once("input string~"); //Allocates the max space required for the output string, instead of the exact. Might be faster.

Interface documentation

The 2 exported objects are Kana and Salt. Kana's constructor expects between 0 and 2 arguments.

• The first is either an algorithm definition or empty, if empty Kana uses the default algorithm (truncated SHA256).
• The second is either an instance of Salt or empty, if empty Kana uses the default library salt.

Salt's constructor expects 0 or 1 argument.

• Either a string to use as the specific salt or empty, if empty there is no salt.

Kana also has a static function single(algo, salt, input) which automatically creates a context, computes the hash, frees the context, and then returns the computed hash as a JavaScript string.

Defined constants

Name	Type	Description
Kana.ALGO_DEFAULT	Algorithm definition	The default algorithm specified by the library (set to sha256 truncated)
Kana.ALGO_CRC32	Algorithm definition	CRC32 checksum algorithm
Kana.ALGO_CRC64	Algorithm definition	CRC64 checksum algorithm
Kana.ALGO_SHA256	Algorithm definition	SHA256 hashing algorithm
Kana.ALGO_SHA256_TRUNCATED	Algorithm definition	Truncated SHA256 algorithm, to 64-bits
Salt.None	Salt	No salt
Salt.Random	Salt	A cryptographically secure random salt
Salt.Default	Salt	The library's default static salt

Notes

The strings generated by this library are meant to be pretty, not secure. It is not a secure way of representing a hash as many collisions are possible.

Digest algorithm

The kana algorithm is a 16-bit block digest that works as follows:

• The most and least significant 8 bits are each seperated into Stage 0 and Stage 1 each operating on the first and second byte respectively.

• Stage 0:

  1. The byte is sign tested (bitwise AND 0x80), store this as a boolean in sign0.
  2. The valid first character range is looked up using the result of the sign test (either 0 or 1), store the range in range, and the slice KANA taken from the range in kana.
  3. The first index is calculated as the unsigned first byte modulo the size (exclusive) of range. Store this as index0.
  4. The swap table is checked to see if index0 has an entry. Then each following step is checked in order:

• If the swap entry exists and the first byte bitwise AND 0x2 is not 0, set the first character of the output to the value found in the swap table.
• If the swap entry exists and the first byte bitwise AND 0x8 is not 0 and the index has an entry in the 2nd swap table, set the first character of the output to the value found in the 2nd swap table.

• In any other case, set the first character of the output to the value found in the kana slice at the index.

  • Stage 1:

    1. Compute a sub table for index plus the start of range using the ranges defined in KANA_SUB_VALID_FOR and store it in sub. If there is no sub table possible, skip to step 3.
    2. If there is an entry in sub for the index of the 2nd byte modulo the size of KANA_SUB, set the second output character to be that character.
    3. If there was no value set from the sub table, the 2nd output character becomes the first output character from inputting the 2nd byte back through Stage 0 as the first byte.
  • Concatenate both characters and move to the next 16-bit block.

  Notes:

  • It is valid for a single iterator to produce between 0 and 2 characters but no more.
  • If an input given to the algorithm that cannot be divided exactly into 16-bit blocks (i.e. one byte is left over), a padding byte of 0 is added as the 2nd byte to make it fit.

  For more information see mnemonic.rs.

License

GPL'd with love <3