/*
 * Description: This module provides ParallelHash functions
 * [NIST-SP-800-185 Section 6].
 */

module algorithms::TupleHash::Main where

import algorithms::Keccak::derived (left_encode, right_encode)
import algorithms::Keccak::Main (bitReordering)
import algorithms::cSHAKE::Main (cSHAKE128, cSHAKE256)

/**
 * ParallelHash supports the efficient hashing of very long strings,
 * by taking advantage of the parallelism available in modern
 * processors. ParallelHash supports the 128- and 256-bit security
 * strengths, and also provides variable-length output. Changing any
 * input parameter to ParallelHash, even the requested output length,
 * will result in unrelated output [NIST-SP-800-185 Section 6.1].
 *
 * Inputs:
 *   `X`: The main input bit string. It may be of any length,
 *        including zero, so long as the length is divisible by `B`
 *        and 8.
 *   `S`: A customization bit string of any length, including zero. If
 *        no customization is desired, set `S` to the empty string.
 *
 * Notable types:
 *   `L`: An integer representing the requested output length in
 *        bits.
 *   `B`: The block size in bytes for parallel hashing. It may be any
 *        integer such that `0 < B < 2 ^^ 2040`.
 */
ParallelHash128 :
    { L, B, n, s }
    ( L < 2 ^^ 2040
    , 0 < B, B < 2 ^^ 2040
    , n < 2 ^^ 2040
    , s < 2 ^^ 2040 )
 => [n * B * 8] -> [s] -> [L]
ParallelHash128 X S =
    cSHAKE128`{L} newX (join "ParallelHash") S
  where
    newX = (bitReordering left_encode`{B})
         # join (parmap (\Xi -> cSHAKE128`{256} Xi [] [])
                        (split`{n, B * 8} X))
         # (bitReordering right_encode`{n})
         # (bitReordering right_encode`{L})

/**
 * ParallelHash supports the efficient hashing of very long strings,
 * by taking advantage of the parallelism available in modern
 * processors. ParallelHash supports the 128- and 256-bit security
 * strengths, and also provides variable-length output. Changing any
 * input parameter to ParallelHash, even the requested output length,
 * will result in unrelated output [NIST-SP-800-185 Section 6.1].
 *
 * Inputs:
 *   `X`: The main input bit string. It may be of any length,
 *        including zero, so long as the length is divisible by `B`
 *        and 8.
 *   `S`: A customization bit string of any length, including zero. If
 *        no customization is desired, set `S` to the empty string.
 *
 * Notable types:
 *   `L`: An integer representing the requested output length in
 *        bits.
 *   `B`: The block size in bytes for parallel hashing. It may be any
 *        integer such that `0 < B < 2 ^^ 2040`.
 */
ParallelHash256 :
    { L, B, n, s }
    ( L < 2 ^^ 2040
    , 0 < B, B < 2 ^^ 2040
    , n < 2 ^^ 2040
    , s < 2 ^^ 2040 )
 => [n * B * 8] -> [s] -> [L]
ParallelHash256 X S =
    cSHAKE256`{L} newX (join "ParallelHash") S
  where
    newX = (bitReordering left_encode`{B})
         # join (parmap (\Xi -> cSHAKE256`{512} Xi [] [])
                        (split`{n, B * 8} X))
         # (bitReordering right_encode`{n})
         # (bitReordering right_encode`{L})

/**
 * This is a variant of `ParallelHash128` as an XOF [NIST-SP-800-185
 * Section 6.3.1].
 *
 * Inputs:
 *   `X`: The main input bit string. It may be of any length,
 *        including zero, so long as the length is divisible by `B`
 *        and 8.
 *   `S`: A customization bit string of any length, including zero. If
 *        no customization is desired, set `S` to the empty string.
 *
 * Notable types:
 *   `L`: An integer representing the requested output length in
 *        bits.
 *   `B`: The block size in bytes for parallel hashing. It may be any
 *        integer such that `0 < B < 2 ^^ 2040`.
 */
ParallelHashXOF128 :
    { L, B, n, s }
    ( 0 < B, B < 2 ^^ 2040
    , n < 2 ^^ 2040
    , s < 2 ^^ 2040 )
 => [n * B * 8] -> [s] -> [L]
ParallelHashXOF128 X S =
    cSHAKE128`{L} newX (join "ParallelHash") S
  where
    newX = (bitReordering left_encode`{B})
         # join (parmap (\Xi -> cSHAKE128`{256} Xi [] [])
                        (split`{n, B * 8} X))
         # (bitReordering right_encode`{n})
         # (bitReordering right_encode`{0})

/**
 * This is a variant of `ParallelHash256` as an XOF [NIST-SP-800-185
 * Section 6.3.1].
 *
 * Inputs:
 *   `X`: The main input bit string. It may be of any length,
 *        including zero, so long as the length is divisible by `B`
 *        and 8.
 *   `S`: A customization bit string of any length, including zero. If
 *        no customization is desired, set `S` to the empty string.
 *
 * Notable types:
 *   `L`: An integer representing the requested output length in
 *        bits.
 *   `B`: The block size in bytes for parallel hashing. It may be any
 *        integer such that `0 < B < 2 ^^ 2040`.
 */
ParallelHashXOF256 :
    { L, B, n, s }
    ( 0 < B, B < 2 ^^ 2040
    , n < 2 ^^ 2040
    , s < 2 ^^ 2040 )
 => [n * B * 8] -> [s] -> [L]
ParallelHashXOF256 X S =
    cSHAKE256`{L} newX (join "ParallelHash") S
  where
    newX = (bitReordering left_encode`{B})
         # join (parmap (\Xi -> cSHAKE256`{512} Xi [] [])
                        (split`{n, B * 8} X))
         # (bitReordering right_encode`{n})
         # (bitReordering right_encode`{0})