2 * Copyright © 2011, 2014
3 * Thorsten Glaser <tg@mirbsd.org>
5 * Provided that these terms and disclaimer and all copyright notices
6 * are retained or reproduced in an accompanying document, permission
7 * is granted to deal in this work without restriction, including un‐
8 * limited rights to use, publicly perform, distribute, sell, modify,
9 * merge, give away, or sublicence.
11 * This work is provided “AS IS” and WITHOUT WARRANTY of any kind, to
12 * the utmost extent permitted by applicable law, neither express nor
13 * implied; without malicious intent or gross negligence. In no event
14 * may a licensor, author or contributor be held liable for indirect,
15 * direct, other damage, loss, or other issues arising in any way out
16 * of dealing in the work, even if advised of the possibility of such
17 * damage or existence of a defect, except proven that it results out
18 * of said person’s immediate fault when using the work as intended.
20 * This file provides BAFH (Better Avalanche for the Jenkins Hash) as
21 * inline macro bodies that operate on “register uint32_t” variables,
22 * with variants that use their local intermediate registers.
24 * Usage note for BAFH with entropy distribution: input up to 4 bytes
25 * is best combined into a 32-bit unsigned integer, which is then run
26 * through BAFHFinish_reg for mixing and then used as context instead
27 * of 0. Longer input should be handled the same: take the first four
28 * bytes as IV after mixing then add subsequent bytes the same way.
29 * This needs counting input bytes and is endian-dependent, thus not,
30 * for speed reasons, specified for the regular stable hash, but very
31 * much recommended if the actual output value may differ across runs
32 * (so is using a random value instead of 0 for the IV).
35 #ifndef SYSKERN_MIRHASH_H
36 #define SYSKERN_MIRHASH_H 1
37 #define SYSKERN_MIRHASH_BAFH
39 #include <sys/types.h>
41 __RCSID("$MirOS: src/bin/mksh/mirhash.h,v 1.2 2014/06/29 11:48:05 tg Exp $");
44 * BAFH itself is defined by the following primitives:
46 * • BAFHInit(ctx) initialises the hash context, which consists of a
47 * sole 32-bit unsigned integer (ideally in a register), to 0.
48 * It is possible to use any initial value out of [0; 2³²[ – which
49 * is, in fact, recommended if using BAFH for entropy distribution
50 * – but for a regular stable hash, the IV 0 is needed.
52 * • BAFHUpdateOctet(ctx,val) compresses the unsigned 8-bit quantity
53 * into the hash context. The algorithm used is Jenkins’ one-at-a-
54 * time, except that an additional constant 1 is added so that, if
55 * the context is (still) zero, adding a NUL byte is not ignored.
57 * • BAFHror(eax,cl) evaluates to the unsigned 32-bit integer “eax”,
58 * rotated right by “cl” ∈ [0;31]; no casting, be careful!
60 * • BAFHFinish(ctx) avalanches the context around so every sub-byte
61 * depends on all input octets; afterwards, the context variable’s
62 * value is the hash output. BAFH does not use any padding, nor is
63 * the input length added; this is due to the common use case (for
64 * quick entropy distribution and use with a hashtable).
65 * Warning: BAFHFinish uses the MixColumn algorithm of AES – which
66 * is reversible (to avoid introducing funnels and reducing entro‐
67 * py), so blinding may need to be employed for some uses, e.g. in
70 * The BAFHUpdateOctet and BAFHFinish are available in two flavours:
71 * suffixed with _reg (assumes the context is in a register) or _mem
74 * The following high-level macros (with _reg and _mem variants) are
77 * • BAFHUpdateMem(ctx,buf,len) adds a memory block to a context.
78 * • BAFHUpdateStr(ctx,buf) is equivalent to using len=strlen(buf).
79 * • BAFHHostMem(ctx,buf,len) calculates the hash of the memory buf‐
80 * fer using the first 4 octets (mixed) for IV, as outlined above;
81 * the result is endian-dependent; “ctx” assumed to be a register.
82 * • BAFHHostStr(ctx,buf) does the same for C strings.
84 * All macros may use ctx multiple times in their expansion, but all
85 * other arguments are always evaluated at most once.
87 * To stay portable, never use the BAFHHost*() macros (these are for
88 * host-local entropy shuffling), and encode numbers using ULEB128.
91 #define BAFHInit(h) do { \
93 } while (/* CONSTCOND */ 0)
95 #define BAFHUpdateOctet_reg(h,b) do { \
96 (h) += (uint8_t)(b); \
100 } while (/* CONSTCOND */ 0)
102 #define BAFHUpdateOctet_mem(m,b) do { \
103 register uint32_t BAFH_h = (m); \
105 BAFHUpdateOctet_reg(BAFH_h, (b)); \
107 } while (/* CONSTCOND */ 0)
109 #define BAFHror(eax,cl) (((eax) >> (cl)) | ((eax) << (32 - (cl))))
111 #define BAFHFinish_reg(h) do { \
112 register uint32_t BAFHFinish_v; \
114 BAFHFinish_v = ((h) >> 7) & 0x01010101U; \
115 BAFHFinish_v += BAFHFinish_v << 1; \
116 BAFHFinish_v += BAFHFinish_v << 3; \
117 BAFHFinish_v ^= ((h) << 1) & 0xFEFEFEFEU; \
119 BAFHFinish_v ^= BAFHror(BAFHFinish_v, 8); \
120 BAFHFinish_v ^= ((h) = BAFHror((h), 8)); \
121 BAFHFinish_v ^= ((h) = BAFHror((h), 8)); \
122 (h) = BAFHror((h), 8) ^ BAFHFinish_v; \
123 } while (/* CONSTCOND */ 0)
125 #define BAFHFinish_mem(m) do { \
126 register uint32_t BAFHFinish_v, BAFH_h = (m); \
128 BAFHFinish_v = (BAFH_h >> 7) & 0x01010101U; \
129 BAFHFinish_v += BAFHFinish_v << 1; \
130 BAFHFinish_v += BAFHFinish_v << 3; \
131 BAFHFinish_v ^= (BAFH_h << 1) & 0xFEFEFEFEU; \
133 BAFHFinish_v ^= BAFHror(BAFHFinish_v, 8); \
134 BAFHFinish_v ^= (BAFH_h = BAFHror(BAFH_h, 8)); \
135 BAFHFinish_v ^= (BAFH_h = BAFHror(BAFH_h, 8)); \
136 (m) = BAFHror(BAFH_h, 8) ^ BAFHFinish_v; \
137 } while (/* CONSTCOND */ 0)
139 #define BAFHUpdateMem_reg(h,p,z) do { \
140 register const uint8_t *BAFHUpdate_p; \
141 register size_t BAFHUpdate_z = (z); \
143 BAFHUpdate_p = (const void *)(p); \
144 while (BAFHUpdate_z--) \
145 BAFHUpdateOctet_reg((h), *BAFHUpdate_p++); \
146 } while (/* CONSTCOND */ 0)
148 /* meh should have named them _r/m but that’s not valid C */
149 #define BAFHUpdateMem_mem(m,p,z) do { \
150 register uint32_t BAFH_h = (m); \
152 BAFHUpdateMem_reg(BAFH_h, (p), (z)); \
154 } while (/* CONSTCOND */ 0)
156 #define BAFHUpdateStr_reg(h,s) do { \
157 register const uint8_t *BAFHUpdate_s; \
158 register uint8_t BAFHUpdate_c; \
160 BAFHUpdate_s = (const void *)(s); \
161 while ((BAFHUpdate_c = *BAFHUpdate_s++) != 0) \
162 BAFHUpdateOctet_reg((h), BAFHUpdate_c); \
163 } while (/* CONSTCOND */ 0)
165 #define BAFHUpdateStr_mem(m,s) do { \
166 register uint32_t BAFH_h = (m); \
168 BAFHUpdateStr_reg(BAFH_h, (s)); \
170 } while (/* CONSTCOND */ 0)
172 #define BAFHHostMem(h,p,z) do { \
173 register const uint8_t *BAFHUpdate_p; \
174 register size_t BAFHUpdate_z = (z); \
181 BAFHUpdate_p = (const void *)(p); \
182 BAFHHost_v.as_u32 = 0; \
183 BAFHHost_z = BAFHUpdate_z < 4 ? BAFHUpdate_z : 4; \
184 memcpy(BAFHHost_v.as_u8, BAFHUpdate_p, BAFHHost_z); \
185 BAFHUpdate_p += BAFHHost_z; \
186 BAFHUpdate_z -= BAFHHost_z; \
187 (h) = BAFHHost_v.as_u32; \
189 while (BAFHUpdate_z--) \
190 BAFHUpdateOctet_reg((h), *BAFHUpdate_p++); \
192 } while (/* CONSTCOND */ 0)
194 #define BAFHHostStr(h,s) do { \
195 register const uint8_t *BAFHUpdate_s; \
196 register uint8_t BAFHUpdate_c; \
202 BAFHUpdate_s = (const void *)(s); \
203 if ((BAFHHost_v.as_u8[0] = *BAFHUpdate_s) != 0) \
205 if ((BAFHHost_v.as_u8[1] = *BAFHUpdate_s) != 0) \
207 if ((BAFHHost_v.as_u8[2] = *BAFHUpdate_s) != 0) \
209 if ((BAFHHost_v.as_u8[3] = *BAFHUpdate_s) != 0) \
211 (h) = BAFHHost_v.as_u32; \
213 while ((BAFHUpdate_c = *BAFHUpdate_s++) != 0) \
214 BAFHUpdateOctet_reg((h), BAFHUpdate_c); \
216 } while (/* CONSTCOND */ 0)