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HalfSipHash, or hsiphash, is a shortened version of SipHash, which generates 32-bit outputs using a weaker 64-bit key. It has *much* lower security margins, and shouldn't be used for anything too sensitive, but it could be used as a hashtable key function replacement, if the output is never exposed, and if the security requirement is not too high. The goal is to make this something that performance-critical jhash users would be willing to use. On 64-bit machines, HalfSipHash1-3 is slower than SipHash1-3, so we alias SipHash1-3 to HalfSipHash1-3 on those systems. 64-bit x86_64: [ 0.509409] test_siphash: SipHash2-4 cycles: 4049181 [ 0.510650] test_siphash: SipHash1-3 cycles: 2512884 [ 0.512205] test_siphash: HalfSipHash1-3 cycles: 3429920 [ 0.512904] test_siphash: JenkinsHash cycles: 978267 So, we map hsiphash() -> SipHash1-3 32-bit x86: [ 0.509868] test_siphash: SipHash2-4 cycles: 14812892 [ 0.513601] test_siphash: SipHash1-3 cycles: 9510710 [ 0.515263] test_siphash: HalfSipHash1-3 cycles: 3856157 [ 0.515952] test_siphash: JenkinsHash cycles: 1148567 So, we map hsiphash() -> HalfSipHash1-3 hsiphash() is roughly 3 times slower than jhash(), but comes with a considerable security improvement. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Reviewed-by: Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
141 lines
4.5 KiB
C
141 lines
4.5 KiB
C
/* Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
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*
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* This file is provided under a dual BSD/GPLv2 license.
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*
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* SipHash: a fast short-input PRF
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* https://131002.net/siphash/
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*
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* This implementation is specifically for SipHash2-4 for a secure PRF
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* and HalfSipHash1-3/SipHash1-3 for an insecure PRF only suitable for
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* hashtables.
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*/
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#ifndef _LINUX_SIPHASH_H
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#define _LINUX_SIPHASH_H
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#include <linux/types.h>
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#include <linux/kernel.h>
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#define SIPHASH_ALIGNMENT __alignof__(u64)
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typedef struct {
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u64 key[2];
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} siphash_key_t;
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u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key);
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#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
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u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key);
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#endif
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u64 siphash_1u64(const u64 a, const siphash_key_t *key);
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u64 siphash_2u64(const u64 a, const u64 b, const siphash_key_t *key);
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u64 siphash_3u64(const u64 a, const u64 b, const u64 c,
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const siphash_key_t *key);
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u64 siphash_4u64(const u64 a, const u64 b, const u64 c, const u64 d,
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const siphash_key_t *key);
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u64 siphash_1u32(const u32 a, const siphash_key_t *key);
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u64 siphash_3u32(const u32 a, const u32 b, const u32 c,
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const siphash_key_t *key);
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static inline u64 siphash_2u32(const u32 a, const u32 b,
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const siphash_key_t *key)
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{
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return siphash_1u64((u64)b << 32 | a, key);
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}
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static inline u64 siphash_4u32(const u32 a, const u32 b, const u32 c,
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const u32 d, const siphash_key_t *key)
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{
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return siphash_2u64((u64)b << 32 | a, (u64)d << 32 | c, key);
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}
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static inline u64 ___siphash_aligned(const __le64 *data, size_t len,
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const siphash_key_t *key)
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{
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if (__builtin_constant_p(len) && len == 4)
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return siphash_1u32(le32_to_cpup((const __le32 *)data), key);
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if (__builtin_constant_p(len) && len == 8)
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return siphash_1u64(le64_to_cpu(data[0]), key);
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if (__builtin_constant_p(len) && len == 16)
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return siphash_2u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
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key);
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if (__builtin_constant_p(len) && len == 24)
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return siphash_3u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
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le64_to_cpu(data[2]), key);
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if (__builtin_constant_p(len) && len == 32)
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return siphash_4u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
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le64_to_cpu(data[2]), le64_to_cpu(data[3]),
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key);
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return __siphash_aligned(data, len, key);
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}
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/**
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* siphash - compute 64-bit siphash PRF value
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* @data: buffer to hash
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* @size: size of @data
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* @key: the siphash key
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*/
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static inline u64 siphash(const void *data, size_t len,
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const siphash_key_t *key)
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{
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#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
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if (!IS_ALIGNED((unsigned long)data, SIPHASH_ALIGNMENT))
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return __siphash_unaligned(data, len, key);
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#endif
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return ___siphash_aligned(data, len, key);
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}
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#define HSIPHASH_ALIGNMENT __alignof__(unsigned long)
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typedef struct {
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unsigned long key[2];
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} hsiphash_key_t;
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u32 __hsiphash_aligned(const void *data, size_t len,
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const hsiphash_key_t *key);
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#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
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u32 __hsiphash_unaligned(const void *data, size_t len,
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const hsiphash_key_t *key);
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#endif
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u32 hsiphash_1u32(const u32 a, const hsiphash_key_t *key);
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u32 hsiphash_2u32(const u32 a, const u32 b, const hsiphash_key_t *key);
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u32 hsiphash_3u32(const u32 a, const u32 b, const u32 c,
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const hsiphash_key_t *key);
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u32 hsiphash_4u32(const u32 a, const u32 b, const u32 c, const u32 d,
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const hsiphash_key_t *key);
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static inline u32 ___hsiphash_aligned(const __le32 *data, size_t len,
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const hsiphash_key_t *key)
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{
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if (__builtin_constant_p(len) && len == 4)
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return hsiphash_1u32(le32_to_cpu(data[0]), key);
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if (__builtin_constant_p(len) && len == 8)
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return hsiphash_2u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
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key);
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if (__builtin_constant_p(len) && len == 12)
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return hsiphash_3u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
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le32_to_cpu(data[2]), key);
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if (__builtin_constant_p(len) && len == 16)
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return hsiphash_4u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
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le32_to_cpu(data[2]), le32_to_cpu(data[3]),
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key);
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return __hsiphash_aligned(data, len, key);
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}
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/**
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* hsiphash - compute 32-bit hsiphash PRF value
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* @data: buffer to hash
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* @size: size of @data
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* @key: the hsiphash key
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*/
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static inline u32 hsiphash(const void *data, size_t len,
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const hsiphash_key_t *key)
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{
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#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
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if (!IS_ALIGNED((unsigned long)data, HSIPHASH_ALIGNMENT))
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return __hsiphash_unaligned(data, len, key);
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#endif
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return ___hsiphash_aligned(data, len, key);
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}
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#endif /* _LINUX_SIPHASH_H */
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