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Message-ID: <20251211011846.8179-2-ebiggers@kernel.org>
Date: Wed, 10 Dec 2025 17:18:33 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: linux-crypto@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
Ard Biesheuvel <ardb@...nel.org>,
"Jason A . Donenfeld" <Jason@...c4.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
linux-arm-kernel@...ts.infradead.org,
x86@...nel.org,
Eric Biggers <ebiggers@...nel.org>
Subject: [PATCH 01/12] lib/crypto: nh: Add NH library
Add support for the NH "almost-universal hash function" to lib/crypto/,
specifically the variant of NH used in Adiantum.
This will replace the need for the "nhpoly1305" crypto_shash algorithm.
All the implementations of "nhpoly1305" use architecture-optimized code
only for the NH stage; they just use the generic C Poly1305 code for the
Poly1305 stage. We can achieve the same result in a simpler way using
an (architecture-optimized) nh() function combined with code in
crypto/adiantum.c that passes the results to the Poly1305 library.
This commit begins this cleanup by adding the nh() function. The code
is derived from crypto/nhpoly1305.c and include/crypto/nhpoly1305.h.
Signed-off-by: Eric Biggers <ebiggers@...nel.org>
---
include/crypto/nh.h | 52 ++++++++++++++++++++++++++++
lib/crypto/Kconfig | 10 ++++++
lib/crypto/Makefile | 8 +++++
lib/crypto/nh.c | 82 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 152 insertions(+)
create mode 100644 include/crypto/nh.h
create mode 100644 lib/crypto/nh.c
diff --git a/include/crypto/nh.h b/include/crypto/nh.h
new file mode 100644
index 000000000000..465e85bf203f
--- /dev/null
+++ b/include/crypto/nh.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * NH hash function for Adiantum
+ */
+
+#ifndef _CRYPTO_NH_H
+#define _CRYPTO_NH_H
+
+#include <linux/types.h>
+
+/* NH parameterization: */
+
+/* Endianness: little */
+/* Word size: 32 bits (works well on NEON, SSE2, AVX2) */
+
+/* Stride: 2 words (optimal on ARM32 NEON; works okay on other CPUs too) */
+#define NH_PAIR_STRIDE 2
+#define NH_MESSAGE_UNIT (NH_PAIR_STRIDE * 2 * sizeof(u32))
+
+/* Num passes (Toeplitz iteration count): 4, to give ε = 2^{-128} */
+#define NH_NUM_PASSES 4
+#define NH_HASH_BYTES (NH_NUM_PASSES * sizeof(u64))
+
+/* Max message size: 1024 bytes (32x compression factor) */
+#define NH_NUM_STRIDES 64
+#define NH_MESSAGE_WORDS (NH_PAIR_STRIDE * 2 * NH_NUM_STRIDES)
+#define NH_MESSAGE_BYTES (NH_MESSAGE_WORDS * sizeof(u32))
+#define NH_KEY_WORDS (NH_MESSAGE_WORDS + \
+ NH_PAIR_STRIDE * 2 * (NH_NUM_PASSES - 1))
+#define NH_KEY_BYTES (NH_KEY_WORDS * sizeof(u32))
+
+/**
+ * nh() - NH hash function for Adiantum
+ * @key: The key. @message_len + 48 bytes of it are used. This is NH_KEY_BYTES
+ * if @message_len has its maximum length of NH_MESSAGE_BYTES.
+ * @message: The message
+ * @message_len: The message length in bytes. Must be a multiple of 16
+ * (NH_MESSAGE_UNIT) and at most 1024 (NH_MESSAGE_BYTES).
+ * @hash: (output) The resulting hash value
+ *
+ * Note: the pseudocode for NH in the Adiantum paper iterates over 1024-byte
+ * segments of the message, computes a 32-byte hash for each, and returns all
+ * the hashes concatenated together. In contrast, this function just hashes one
+ * segment and returns one hash. It's the caller's responsibility to call this
+ * function for each 1024-byte segment and collect all the hashes.
+ *
+ * Context: Any context.
+ */
+void nh(const u32 *key, const u8 *message, size_t message_len,
+ __le64 hash[NH_NUM_PASSES]);
+
+#endif /* _CRYPTO_NH_H */
diff --git a/lib/crypto/Kconfig b/lib/crypto/Kconfig
index ee6ab129d0cf..f14c9f5974d8 100644
--- a/lib/crypto/Kconfig
+++ b/lib/crypto/Kconfig
@@ -106,10 +106,20 @@ config CRYPTO_LIB_MLDSA
select CRYPTO_LIB_SHA3
help
The ML-DSA library functions. Select this if your module uses any of
the functions from <crypto/mldsa.h>.
+config CRYPTO_LIB_NH
+ tristate
+ help
+ Implementation of the NH almost-universal hash function, specifically
+ the variant of NH used in Adiantum.
+
+config CRYPTO_LIB_NH_ARCH
+ bool
+ depends on CRYPTO_LIB_NH && !UML
+
config CRYPTO_LIB_POLY1305
tristate
help
The Poly1305 library functions. Select this if your module uses any
of the functions from <crypto/poly1305.h>.
diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index a0578105266f..929b84568809 100644
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -129,10 +129,18 @@ endif # CONFIG_CRYPTO_LIB_MD5_ARCH
obj-$(CONFIG_CRYPTO_LIB_MLDSA) += libmldsa.o
libmldsa-y := mldsa.o
################################################################################
+obj-$(CONFIG_CRYPTO_LIB_NH) += libnh.o
+libnh-y := nh.o
+ifeq ($(CONFIG_CRYPTO_LIB_NH_ARCH),y)
+CFLAGS_nh.o += -I$(src)/$(SRCARCH)
+endif
+
+################################################################################
+
obj-$(CONFIG_CRYPTO_LIB_POLY1305) += libpoly1305.o
libpoly1305-y := poly1305.o
ifeq ($(CONFIG_ARCH_SUPPORTS_INT128),y)
libpoly1305-$(CONFIG_CRYPTO_LIB_POLY1305_GENERIC) += poly1305-donna64.o
else
diff --git a/lib/crypto/nh.c b/lib/crypto/nh.c
new file mode 100644
index 000000000000..e1d0095b5289
--- /dev/null
+++ b/lib/crypto/nh.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018 Google LLC
+ */
+
+/*
+ * Implementation of the NH almost-universal hash function, specifically the
+ * variant of NH used in Adiantum. This is *not* a cryptographic hash function.
+ *
+ * Reference: section 6.3 of "Adiantum: length-preserving encryption for
+ * entry-level processors" (https://eprint.iacr.org/2018/720.pdf).
+ */
+
+#include <crypto/nh.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/unaligned.h>
+
+#ifdef CONFIG_CRYPTO_LIB_NH_ARCH
+#include "nh.h" /* $(SRCARCH)/nh.h */
+#else
+static bool nh_arch(const u32 *key, const u8 *message, size_t message_len,
+ __le64 hash[NH_NUM_PASSES])
+{
+ return false;
+}
+#endif
+
+void nh(const u32 *key, const u8 *message, size_t message_len,
+ __le64 hash[NH_NUM_PASSES])
+{
+ u64 sums[4] = { 0, 0, 0, 0 };
+
+ if (nh_arch(key, message, message_len, hash))
+ return;
+
+ static_assert(NH_PAIR_STRIDE == 2);
+ static_assert(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]);
+ message += NH_MESSAGE_UNIT;
+ message_len -= NH_MESSAGE_UNIT;
+ }
+
+ hash[0] = cpu_to_le64(sums[0]);
+ hash[1] = cpu_to_le64(sums[1]);
+ hash[2] = cpu_to_le64(sums[2]);
+ hash[3] = cpu_to_le64(sums[3]);
+}
+EXPORT_SYMBOL_GPL(nh);
+
+#ifdef nh_mod_init_arch
+static int __init nh_mod_init(void)
+{
+ nh_mod_init_arch();
+ return 0;
+}
+subsys_initcall(nh_mod_init);
+
+static void __exit nh_mod_exit(void)
+{
+}
+module_exit(nh_mod_exit);
+#endif
+
+MODULE_DESCRIPTION("NH almost-universal hash function");
+MODULE_LICENSE("GPL");
--
2.52.0
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