linux-imx

// SPDX-License-Identifier: GPL-2.0

/*

 * NHPoly1305 - ε-almost-∆-universal hash function for Adiantum

 *

 * Copyright 2018 Google LLC

 */

​

/*

 * "NHPoly1305" is the main component of Adiantum hashing.

 * Specifically, it is the calculation

 *

 *  H_L ← Poly1305_{K_L}(NH_{K_N}(pad_{128}(L)))

 *

 * from the procedure in section 6.4 of the Adiantum paper [1].  It is an

 * ε-almost-∆-universal (ε-∆U) hash function for equal-length inputs over

 * Z/(2^{128}Z), where the "∆" operation is addition.  It hashes 1024-byte

 * chunks of the input with the NH hash function [2], reducing the input length

 * by 32x.  The resulting NH digests are evaluated as a polynomial in

 * GF(2^{130}-5), like in the Poly1305 MAC [3].  Note that the polynomial

 * evaluation by itself would suffice to achieve the ε-∆U property; NH is used

 * for performance since it's over twice as fast as Poly1305.

 *

 * This is *not* a cryptographic hash function; do not use it as such!

 *

 * [1] Adiantum: length-preserving encryption for entry-level processors

 *     (https://eprint.iacr.org/2018/720.pdf)

 * [2] UMAC: Fast and Secure Message Authentication

 *     (https://fastcrypto.org/umac/umac_proc.pdf)

 * [3] The Poly1305-AES message-authentication code

 *     (https://cr.yp.to/mac/poly1305-20050329.pdf)

 */

​

#include <asm/unaligned.h>

#include <crypto/algapi.h>

#include <crypto/internal/hash.h>

#include <crypto/nhpoly1305.h>

#include <linux/crypto.h>

#include <linux/kernel.h>

#include <linux/module.h>

​

static void nh_generic(const u32 *key, const u8 *message, size_t message_len,

               __le64 hash[NH_NUM_PASSES])

{

    u64 sums[4] = { 0, 0, 0, 0 };

​

    BUILD_BUG_ON(NH_PAIR_STRIDE != 2);

    BUILD_BUG_ON(NH_NUM_PASSES != 4);

​

    while (message_len) {

        u32 m0 = get_unaligned_le32(message + 0);

        u32 m1 = get_unaligned_le32(message + 4);

        u32 m2 = get_unaligned_le32(message + 8);

        u32 m3 = get_unaligned_le32(message + 12);

​

        sums[0] += (u64)(u32)(m0 + key[ 0]) * (u32)(m2 + key[ 2]);

        sums[1] += (u64)(u32)(m0 + key[ 4]) * (u32)(m2 + key[ 6]);

        sums[2] += (u64)(u32)(m0 + key[ 8]) * (u32)(m2 + key[10]);

        sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]);

        sums[0] += (u64)(u32)(m1 + key[ 1]) * (u32)(m3 + key[ 3]);

        sums[1] += (u64)(u32)(m1 + key[ 5]) * (u32)(m3 + key[ 7]);

        sums[2] += (u64)(u32)(m1 + key[ 9]) * (u32)(m3 + key[11]);

        sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]);

        key += NH_MESSAGE_UNIT / sizeof(key[0]);