Skip to content

rurban/smhasher

Folders and files

NameName
Last commit message
Last commit date

Latest commit

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Repository files navigation

SMhasher

Linux Build status Windows Build status FreeBSD Build status

Hash function MiB/sec cycl./hash cycl./map size Quality problems
donothing32 11536809.55 4.00 - 13 bad seed 0, test NOP
donothing64 12269832.97 4.00 - 13 bad seed 0, test NOP
donothing128 11961841.48 4.08 - 13 bad seed 0, test NOP
NOP_OAAT_read64 11652662.97 14.00 - 47 test NOP
BadHash 794.68 72.80 - 47 bad seed 0, test FAIL
sumhash 10184.67 29.40 - 363 bad seed 0, test FAIL
sumhash32 44755.87 23.46 - 863 UB, test FAIL
multiply_shift 8286.63 25.39 209.06 (2) 345 bad seeds & 0xfffffff0, fails most tests
pair_multiply_shift 5728.05 39.67 218.48 (12) 609 fails most tests
--------------------------
crc32 369.88 142.33 396.81 (101) 422 insecure, 8590x collisions, distrib, PerlinNoise
md5_32 359.43 638.92 865.21 (6) 4419
md5_64 360.20 640.38 869.55 (6) 4419
md5-128 344.63 669.59 856.34 (5) 4419
sha1_32 353.03 1385.80 1759.94 (5) 5126 Sanity, Cyclic low32, 36.6% distrib
sha1_64 353.03 1385.80 1759.94 (5) 5126 Sanity, Cyclic low32, 36.6% distrib
sha1-160 364.95 1470.55 1794.16 (13) 5126 Comb/Cyclic low32
sha2-224 147.13 1354.81 1589.92 (12) Comb low32
sha2-224_64 147.60 1360.10 1620.93 (13) Cyclic low32
sha2-256 147.80 1374.90 1606.06 (16)
sha2-256_64 148.01 1376.34 1624.71 (16)
sha1ni 1632.88 170.77 379.84 (5) 989 insecure,sanity, Permutation, Zeroes, machine-specific
sha1ni_32 1583.50 172.17 387.70 (4) 989 machine-specific
sha2ni-256 1556.66 180.75 393.79 (5) 4241 insecure,sanity, Permutation, Zeroes, machine-specific
sha2ni-256_64 1508.82 184.89 393.07 (6) 4241 Zeroes, machine-specific
blake3_c 1298.04 354.25 563.63 (4) no 32bit portability
rmd128 294.42 712.67 930.65 (4)
rmd160 202.16 1045.79 1287.74 (16) Cyclic hi32
rmd256 366.21 615.39 830.04 (7)
edonr224 863.77 304.76 496.66 (3)
edonr256 870.97 296.40 517.82 (6)
blake2s-128 295.30 698.09 1059.24 (51)
blake2s-160 215.01 1026.74 1239.54 (11)
blake2s-224 207.06 1063.86 1236.50 (20)
blake2s-256 215.28 1014.88 1230.38 (28)
blake2s-256_64 211.52 1044.22 1228.43 (8)
blake2b-160 356.08 1236.84 1458.15 (12)
blake2b-224 356.59 1228.50 1425.87 (16)
blake2b-256 355.97 1232.22 1443.31 (19)
blake2b-256_64 356.97 1222.76 1435.03 (9)
asconhashv12 144.98 885.02 1324.23 (38) 4341
asconhashv12_64 159.33 402.54 473.15 (4) 6490
sha3-256 100.58 3877.18 4159.79 (37) PerlinNoise
sha3-256_64 100.57 3909.00 4174.63 (16) PerlinNoise
hasshe2 2879.93 62.47 272.34 (2) 445 Permutation,TwoBytes,Zeroes,Seed
poly_1_mersenne 1278.37 63.42 244.41 (1) 479 fails most tests
poly_2_mersenne 1391.90 69.97 255.44 (3) 479
poly_3_mersenne 1320.15 80.81 263.12 (2) 479
poly_4_mersenne 1393.93 89.07 262.97 (2) 479
tabulation32 5819.40 40.16 233.00 (3) 848 collisions
tabulation 7407.94 39.83 240.25 (4) 554
crc32_hw 5537.79 40.80 225.65 (3) 653 insecure, 100% bias, collisions, distrib, BIC, machine-specific (SSE4.2/NEON)
crc32_hw1 7626.17 50.21 228.50 (2) 671 insecure, 100% bias, collisions, distrib, BIC, machine-specific (x86 SSE4.2)
crc64_hw 5579.17 40.87 202.19 (1) 652 insecure, 100% bias, collisions, distrib, BIC, machine-specific (SSE4.2/NEON)
crc32_pclmul 7963.20 106.02 567.70 (3) insecure, 100% bias, collisions, distrib, BIC, machine-specific (x86 SSE4.2+PCLMUL)
crc64_jones1 1673.67 83.00 249.16 (2) insecure, 100% bias, collisions, distrib, BIC, machine-specific
crc64_jones2 2968.07 314.60 253.01 (3) insecure, 100% bias, collisions, distrib, BIC, machine-specific
crc64_jones3 3398.80 302.59 258.16 (8) insecure, 100% bias, collisions, distrib, BIC, machine-specific
crc64_jones 3512.66 80.70 251.40 (2) insecure, 100% bias, collisions, distrib, BIC, machine-specific
o1hash 11530366.92 18.40 206.94 (1) 101 insecure, no seed, zeros, fails all tests
fibonacci 15409.62 22.67 872.83 (3) 1692 UB, zeros, fails all tests
FNV1a 754.70 75.28 226.30 (2) 204 bad seed, zeros, fails all tests
FNV1A_Totenschiff 6166.85 26.60 235.71 (2) 270 UB, zeros, fails all tests
FNV1A_Pippip_Yurii 6115.29 28.03 233.52 (2) 147 UB, sanity, fails all tests
FNV1a_YT 13481.70 30.67 233.71 (7) 321 bad seed, UB, fails all tests
FNV2 5630.87 32.09 207.08 (1) 278 fails all tests
FNV64 747.70 74.18 189.18 (1) 79 fails all tests
FNV128 408.59 130.82 299.47 (20) 171 fails all tests
k-hash32 2227.90 53.85 255.78 (2) 808 insecure, zeros, UB, bad seeds, fails all tests
k-hash64 2492.66 48.18 242.58 (2) 609 insecure, zeros, UB, bad seeds, fails all tests
fletcher2 15410.12 20.72 345.55 (5) 248 bad seed 0, UB, fails all tests
fletcher4 15603.68 21.24 320.09 (2) 371 bad seed 0, UB, fails all tests
bernstein 1032.00 59.04 225.09 (3) 41 bad seed 0, fails all tests
sdbm 772.01 71.67 220.09 (2) 41 bad seed 0, fails all tests
x17 765.01 75.61 225.81 (2) 79 99.98% bias, fails all tests
libiberty 618.39 86.58 220.95 (2) 37 insecure, 100% bias, fails all tests, bad seed
gcc 612.10 88.44 224.62 (2) 39 insecure, 100% bias, fails all tests, bad seed
JenkinsOOAT 615.60 111.23 251.08 (2) 153 bad seed 0, 53.5% bias, fails all tests
JenkinsOOAT_perl 631.79 93.13 232.44 (1) 65 bad seed 0, 1.5-11.5% bias, 7.2x collisions, BIC, LongNeighbors
MicroOAAT 730.89 78.25 236.07 (3) 68 100% bias, distrib, BIC
pearsonhash64 439.85 123.07 213.68 (1) Avalanche, Seed, SSSE3 only. broken MSVC
pearsonhash128 438.49 123.81 212.89 (2) Avalanche, Seed, SSSE3 only. broken MSVC
pearsonhash256 440.63 120.72 224.63 (2) Avalanche, Seed, SSSE3 only. broken MSVC
VHASH_32 13084.37 65.45 280.14 (2) 1231 sanity, Seed, MomentChi2
VHASH_64 13217.64 64.90 270.04 (2) 1231 sanity, Seed, Sparse
farsh32 27583.89 65.65 266.64 (2) 944 insecure: AppendedZeroes, collisions+bias, MomentChi2, LongNeighbors
farsh64 13558.69 113.74 327.26 (3) 944 insecure: AppendedZeroes, collisions+bias, MomentChi2, LongNeighbors
farsh128 7055.39 229.42 375.57 (4) 944 insecure: AppendedZeroes, collisions+bias, permut,combin,2bytes,zeroes,PerlinNoise
farsh256 3466.26 444.74 610.23 (4) 944 insecure: AppendedZeroes, collisions+bias, permut,combin,2bytes,zeroes,PerlinNoise
jodyhash32 1762.46 42.66 236.09 (2) 102 bias, collisions, distr, BIC LongNeighbors
jodyhash64 4861.84 44.05 234.35 (2) 118 bias, collisions, distr, BIC, LongNeighbors
lookup3 2474.09 40.19 238.22 (3) 341 UB, 28% bias, collisions, 30% distr, BIC
superfast 2085.79 49.89 230.76 (3) 210 UB, bad seed 0, 91% bias, 5273.01x collisions, 37% distr, BIC
MurmurOAAT 513.75 105.23 244.81 (4) 47 bad seed 0, collisions, 99.998% distr., BIC, LongNeighbors
Crap8 3081.04 37.15 234.94 (2) 342 UB, 2.42% bias, collisions, 2% distrib
Murmur1 1955.36 48.84 236.25 (2) 358 UB, 1 bad seed, 511x collisions, Diff, BIC
Murmur2 3082.03 41.62 250.72 (4) 358 UB, 1 bad seed, 1.7% bias, 81x coll, 1.7% distrib, BIC
Murmur2A 2850.40 46.60 284.58 (13) 407 UB, 1 bad seed, 12.7% bias, LongNeighbors
Murmur2B 6039.96 38.70 212.23 (1) 433 UB, 1.8% bias, collisions, 3.4% distrib, BIC
Murmur2C 3802.68 49.82 220.13 (2) 444 UB, 2^32 bad seeds, 91% bias, collisions, distr, BIC, LongNeighbors
Murmur3A 3027.30 48.99 234.49 (2) 351 UB, 1 bad seed, Moment Chi2 69
PMurHash32 3001.44 48.99 240.35 (3) 1862 1 bad seed, Moment Chi2 69
Murmur3C 4824.95 57.39 243.91 (2) 859 UB, LongNeighbors, Text, DiffDist
mirhash32low 6168.04 38.35 234.32 (2) 1112 UB, 4 bad seeds, Cyclic, LongNeighbors, machine-specific (32/64 differs)
PMPML_32 6904.30 44.25 233.59 (2) 1084 Avalanche >512, unseeded: Seed, BIC, MomentChi2, PerlinNoise
PMPML_64 10030.67 49.22 239.07 (5) 1305 unseeded: Seed, MomentChi2, BIC
xxHash32 6064.37 48.86 234.27 (3) 738 LongNeighbors, collisions with 4bit diff, MomentChi2 220
metrohash64 14209.14 40.85 225.16 (2) 624 UB, LongNeighbors, BIC
metrohash64_1 14495.30 40.83 213.00 (2) 624 UB, LongNeighbors, BIC, MomentChi2
metrohash64crc_1 8010.90 44.43 213.94 (2) 632 UB, Cyclic 8/8 byte, DiffDist, BIC, MomentChi2, machine-specific (SSE4.2/NEON)
metrohash64crc_2 7939.65 44.84 222.01 (2) 632 UB, Cyclic 8/8 byte, DiffDist, BIC, machine-specific (SSE4.2/NEON)
cmetrohash64_1o 14678.56 40.33 216.44 (2) 3506 UB, LongNeighbors, BIC, MomentChi2
cmetrohash64_1 14332.75 41.04 216.05 (2) 652 UB, LongNeighbors, BIC, MomentChi2
City64noSeed 14023.27 33.37 223.59 (2) 1038 Avalanche, Sparse, TwoBytes, MomentChi2, Seed
City64 14390.09 46.69 231.99 (2) 1120 Sparse, TwoBytes
t1ha1_64le 13425.03 31.37 221.97 (2) 517 Avalanche
t1ha1_64be 12002.50 31.57 226.52 (2) 555 Avalanche
t1ha0_32le 7276.16 49.11 236.39 (2) 509 Sparse, LongNeighbors
t1ha0_32be 6860.87 50.16 241.26 (2) 533 Sparse, LongNeighbors
t1ha0_aes_avx1 27881.52 36.78 227.13 (2) 533 Sparse, LongNeighbors
t1ha2_stream 13673.22 81.12 263.88 (3) 1665 Sparse, Permutation, LongNeighbors
t1ha2_stream128 13913.43 94.60 296.15 (4) 1665 Sparse, Permutation, LongNeighbors
aesnihash 5365.60 57.21 255.87 (3) 1209 fails many tests, machine-specific (x64 AES-NI)
aesni-hash-peterrk 29107.73 28.86 217.57 (1) machine-specific (x64 AES-NI)
falkhash 52401.48 122.70 316.79 (4) 264 Sparse, LongNeighbors, machine-specific (x64 AES-NI)
MeowHash 29969.81 64.90 273.79 (8) 1764 Sparse, invertible, machine-specific (x64 AES-NI)
MeowHash64low 29438.45 63.76 269.41 (4) 1764 Sparse, invertible, machine-specific (x64 AES-NI)
MeowHash32low 30562.54 63.77 283.26 (3) 1764 Sparse, invertible, machine-specific (x64 AES-NI)
--------------------------------------
tifuhash_64 35.60 1679.52 1212.75 (15) 276 Cyclic low32
floppsyhash 35.72 1868.92 1411.07 (7) 623
beamsplitter 789.22 682.45 1150.33 (26) 4203 UB
discohash1 4152.62 202.14 414.34 (4) 1294
discohash1-128 4064.39 231.06 430.94 (6) 1294
discohash2 4026.84 204.37 408.13 (6) 1294
discohash2-128 4153.48 226.54 429.24 (4) 1294
discoNONG 3661.23 397.81 651.23 (54) bad seeds
chaskey 1142.38 113.98 288.04 (1) 1609 PerlinNoise
SipHash 953.51 147.32 332.02 (5) 1071
HalfSipHash 1128.85 80.48 260.42 (2) 700 zeroes
GoodOAAT 744.67 87.23 243.36 (2) 237
pearsonbhash64 1749.98 99.84 257.11 (2) 683
pearsonbhash128 1656.68 106.78 276.92 (3) 1134
pearsonbhash256 1418.61 123.68 301.26 (3) 844
prvhash64_64m 3107.77 47.31 236.76 (2) 349
prvhash64_64 3057.79 47.83 244.16 (2) 384
prvhash64_128 3340.87 67.90 264.44 (2) 718
prvhash64s_64 6724.41 266.09 438.90 (3) 2640
prvhash64s_128 6703.66 326.46 508.67 (3) 2799
SipHash13 1803.96 107.93 304.05 (3) 778 0.9% bias
TSip 4330.87 52.43 245.31 (2) 519 !msvc
seahash 8240.58 58.61 260.35 (1) 871 PerlinNoise, !msvc
seahash32low 8245.91 58.61 264.07 (2) 871 PerlinNoise 32, !msvc
clhash 22932.36 67.22 262.78 (2) 1809 PerlinNoise, machine-specific (x64 SSE4.2)
HighwayHash64 6242.58 99.55 248.41 (3) 2546
Murmur3F 7104.08 52.69 216.34 (2) 699 UB
MUM 9631.26 34.78 219.14 (2) 1912 UB, too many bad seeds, machine-specific (32/64 differs)
MUMlow 8532.17 35.95 238.37 (2) 1912 UB, 5 bad seeds
xmsx32 2105.03 45.35 238.92 (3) 192 2 bad seeds
mirhash 5793.85 38.15 212.91 (2) 1112 UB, 2^36 bad seeds, LongNeighbors, machine-specific (32/64 differs)
mirhashstrict 3587.79 49.85 219.49 (2) 1112
mirhashstrict32low 3642.77 50.16 233.34 (3) 1112 1 bad seed, MomentChi2 9
fasthash32 6107.05 40.49 237.83 (2) 566 UB
fasthash64 5600.11 38.04 219.71 (2) 509 UB
aesni 31185.98 29.45 226.75 (2) 519 machine-specific (x64 AES-NI)
aesni-low 31027.39 29.47 232.54 (2) 519 machine-specific (x64 AES-NI)
mx3 9332.99 47.07 221.61 (2) 734 UB
pengyhash 13347.17 74.79 278.74 (3) 421
City32 5745.83 52.44 242.69 (2) 1319
City64low 13119.17 47.92 251.81 (2) 1120
City128 14472.20 88.71 285.61 (10) 1841
CityCrc128 12255.05 89.25 281.85 (2) 295
CityCrc256 12428.45 164.93 358.73 (2)
FarmHash32 22136.14 46.75 258.73 (2) 11489 machine-specific (x64 SSE4/AVX)
FarmHash64 12929.54 46.82 238.50 (2) 3758
FarmHash128 14454.12 68.09 254.04 (2) 163
farmhash32_c 22150.13 46.08 251.43 (3) 762 machine-specific (x64 SSE4/AVX)
farmhash64_c 12925.73 46.76 239.47 (2) 3688
farmhash128_c 14284.69 68.80 256.66 (3) 1890
metrohash64_2 14359.39 41.09 215.53 (2) 627 UB, LongNeighbors
cmetrohash64_2 14498.20 40.87 219.65 (2) 655 LongNeighbors
metrohash128 15847.63 72.33 266.54 (2) 773 UB, LongNeighbors
metrohash128_1 15556.40 73.49 259.05 (2) 773 UB, LongNeighbors
metrohash128_2 15408.56 74.36 259.57 (2) 773 UB, LongNeighbors
metrohash128crc_1 8182.02 77.38 256.80 (2) 723 UB, machine-specific (SSE4.2/NEON)
metrohash128crc_2 7996.33 78.81 262.53 (2) 723 UB, machine-specific (SSE4.2/NEON)
xxHash64 11176.72 49.67 230.24 (6) 1999
Spooky32 13623.84 55.45 248.11 (3) 2221 UB
Spooky64 13400.95 55.06 244.86 (3) 2221 UB
Spooky128 13621.00 59.05 235.42 (2) 2221 UB
SpookyV2_32 13626.51 56.19 256.57 (19) 2069
SpookyV2_64 13401.13 56.18 246.33 (11) 2069
SpookyV2_128 12252.64 58.94 235.46 (2) 2069
ahash64 9862.62 27.32 181.68 (1) 412 rust
xxh3 20853.74 29.46 220.07 (2) 744 DiffDist bit 7 w. 36 bits, BIC
xxh3low 20568.96 29.98 243.82 (5) 756
xxh128 19259.99 31.58 228.84 (2) 1012
xxh128low 19555.88 30.85 227.83 (2) 1012
t1ha2_atonce 14275.60 37.02 224.12 (2) 541 Zeroes low3
t1ha2_atonce128 14059.85 56.44 251.53 (3) 613 LongNeighbors
t1ha0_aes_noavx 27335.47 37.34 230.59 (2) 925 LongNeighbors, machine-specific (x86 AES-NI)
t1ha0_aes_avx1 27881.52 36.78 227.13 (2) 843 LongNeighbors, machine-specific (x64 AVX)
t1ha0_aes_avx2 56581.83 36.51 223.59 (1) 792 LongNeighbors, machine-specific (x64 AVX2)
wyhash32 2532.89 48.40 484.57 (1) 426 4 bad and broken seeds, 32-bit
wyhash32low 23104.85 28.56 239.71 (4) 474 5 bad seeds
wyhash 22640.53 28.91 229.00 (2) 474
w1hash 14208.56 26.85 221.76 (2)
rapidhash 22147.09 29.07 214.80 (2) 574
rapidhash_unrolled 21723.13 29.40 220.97 (3) 782
umash32 21999.19 41.14 239.07 (2) 1530
umash32_hi 22347.33 41.22 251.12 (4) 1530
umash64 21963.54 41.12 228.34 (1) 1530
umash128 13629.66 41.65 228.25 (1) 1530
halftime_hash64 4801.79 99.05 310.02 (2) 2911
halftime_hash128 18220.34 94.31 307.50 (1) 2462
halftime_hash256 18249.32 97.56 322.85 (2) 2622
halftime_hash512 10906.18 118.54 326.76 (3) 3550
nmhash32 12676.08 57.09 255.20 (2) 2445
nmhash32x 13072.64 42.09 288.12 (3) 1494
k-hashv32 8393.09 53.95 252.98 (3) 1280
k-hashv64 9251.05 51.72 251.83 (2) 1279
komihash 12179.74 33.23 224.80 (2) 1323
polymur 9913.53 41.68 232.56 (3) 1128
gxhash32 47943.08 37.71 251.38 (2) 736 AES only
gxhash64 48919.73 36.61 236.98 (3) 720 AES only

The sortable table variants:

Summary

I added some SSE assisted hashes and fast intel/arm CRC32-C, AES and SHA HW variants. See also the old https://github.com/aappleby/smhasher/wiki, the improved, but unmaintained fork https://github.com/demerphq/smhasher, and the new improved version SMHasher3 https://gitlab.com/fwojcik/smhasher3.

So the fastest hash functions on x86_64 without quality problems are:

  • rapidhash (an improved wyhash)
  • xxh3low
  • wyhash
  • umash (even universal!)
  • ahash64
  • t1ha2_atonce
  • komihash
  • FarmHash (not portable, too machine specific: 64 vs 32bit, old gcc, ...)
  • halftime_hash128
  • Spooky32
  • pengyhash
  • nmhash32
  • mx3
  • MUM/mir (different results on 32/64-bit archs, lots of bad seeds to filter out)
  • fasthash32

Hash functions for symbol tables or hash tables typically use 32 bit hashes, for databases, file systems and file checksums typically 64 or 128bit, for crypto now starting with 256 bit.

Typical median key size in perl5 is 20, the most common 4. Similar for all other dynamic languages. See github.com/rurban/perl-hash-stats

When used in a hash table the instruction cache will usually beat the CPU and throughput measured here. In my tests the smallest FNV1A beats the fastest crc32_hw1 with Perl 5 hash tables. Even if those worse hash functions will lead to more collisions, the overall speed advantage and inline-ability beats the slightly worse quality. See e.g. A Seven-Dimensional Analysis of Hashing Methods and its Implications on Query Processing for a concise overview of the best hash table strategies, confirming that the simplest Mult hashing (bernstein, FNV*, x17, sdbm) always beat "better" hash functions (Tabulation, Murmur, Farm, ...) when used in a hash table.

The fast hash functions tested here are recommendable as fast for file digests and maybe bigger databases, but not for 32bit hash tables. The "Quality problems" lead to less uniform distribution, i.e. more collisions and worse performance, but are rarely related to real security attacks, just the 2nd sanity AppendZeroes test against \0 invariance is security relevant.

Columns

MiB/sec: The average of the Bulk key speed test for alignments 0-7 with 262144-byte keys. The higher the better.

cycl./hash: The average of the Small key speed test for 1-31 byte keys. The smaller the better.

cycl./map: The result of the Hashmap test for /usr/dict/words with fast C++ hashmap get queries, with the standard deviation in brackets. This tests the inlinability of the hash function in practise (see size). The smaller the better.

size: The object size in byte on AMD64. This affects the inlinability in e.g. hash tables. The smaller the better.

Quality problems: See the failures in the linked doc. The less the better.

Other

SECURITY

The hash table attacks described in SipHash against City, Murmur or Perl JenkinsOAAT or at Hash Function Lounge are not included here. We list some known attacks at GH #186.

Such an attack avoidance cannot be the problem of the hash function, but only the hash table collision resolution scheme. You can attack every single hash function, even the best and most secure if you detect the seed, e.g. from language (mis-)features, side-channel attacks, collision timings and independly the sort-order, so you need to protect your collision handling scheme from the worst-case O(n), i.e. separate chaining with linked lists. Linked lists chaining allows high load factors, but is very cache-unfriendly. The only recommendable linked list scheme is inlining the key or hash into the array. Nowadays everybody uses fast open addressing, even if the load factor needs to be ~50%, unless you use Cuckoo Hashing.

I.e. the usage of SipHash for their hash table in Python 3.4, ruby, rust, systemd, OpenDNS, Haskell and OpenBSD is pure security theatre. SipHash is not secure enough for security purposes and not fast enough for general usage. Brute-force generation of ~32k collisions need 2-4m for all these hashes. siphash being the slowest needs max 4m, other typically max 2m30s, with <10s for practical 16k collision attacks with all hash functions. Using Murmur is usually slower than a simple Mult, even in the worst case. Provable secure is only uniform hashing, i.e. 2-5 independent Mult or Tabulation, or using a guaranteed logarithmic collision scheme (a tree) or a linear collision scheme, such as swisstable/folly-F14, Robin Hood or Cuckoo hashing with collision counting.

One more note regarding security: Nowadays even SHA1 can be solved in a solver, like Z3 (or faster ones) for practical hash table collision attacks (i.e. 14-20 bits). All hash functions with less than 160 bits tested here cannot be considered "secure" at all.

The '\0' vulnerability attack with binary keys is tested in the 2nd Sanity Zero test.

CRYPTO

Our crypto hashes are hardened with an added size_t seed, mixed into the initial state, and the versions which require zero-padding are hardened by adding the len also, to prevent from collisions with AppendedZeroes for the padding. The libtomcrypt implementations already provide for that, but others might not. Without, such crypto hash functions are unsuitable for normal tasks, as it's trivial to create collisions by padding or bad seeds.

The official NIST hash function testsuite does not do such extensive statistical tests, to search for weak ranges in the bits. Also crypto does not change the initial state, which we do here for our random 32bit seed. Crypto mostly cares about unreversable key -> hash functions without changing the initial fixed state and timings/sidechannel attacks.

The NIST "Cryptographic Algorithm Validation Program" (CAVP) involves the testing of the implementations of FIPS-approved and NIST-recommended cryptographic algorithms. During the NIST SHA-3 competition, the testing methodology was borrowed from the "CAVP", as the KATs and MCTs of the SHA-3 Competition Test Suite were based on the CAVP tests for SHA-2. In addition to this, the “Extremely Long Message Test,” not present in the CAVP for SHA-2, required the submitters to generate the hash value corresponding to a message with a length of 1 GiB. “NIST - Cryptographic Algorithm Validation Program (CAVP),” June 2017. Available: http://csrc.nist.gov/groups/STM/cavp (No testing source code provided, just high-level descriptions)

Two other independent third party testsuites found an extensive number of bugs and weaknesses in the SHA3 candidates. "Finding Bugs in Cryptographic Hash Function Implementations", Nicky Mouha, Mohammad S Raunak, D. Richard Kuhn, and Raghu Kacker, 2017. https://eprint.iacr.org/2017/891.pdf

Maybe independent researchers should come together to do a better public SHA-4 round, based on better and more testing methods, open source code for the tests, and using standard industry practices, such as valgrind, address-sanitizer and ubsan to detect obvious bugs.

PROBLEMS

  • Bad Seeds

    Hash functions are typically initialized with a random seed. But some seed values may lead to bad hash functions, regardless of the key. In the regular case with random seeds the probablity of such bad seeds is very low, like 2^32 or 2^64. A practical application needs to know if bad seeds exist and choose another one. See e.g. mirhash_seed_init() and mirhash_bad_seeds() in Hashes.h. Note that a bad seed is not really a problem when you skip this seed during initialization. It can still be a GOOD or recommended hash function. But a bad seed of 0 leading to collisions is considered a bug, a bad hash function.

    We test for internal secrets, if they will be multiplied with 0. This is also called "blinding multiplication". main.cpp lists some secrets for each hash function we test against. The function <hash>_bad_seeds() lists the confirmed bad seeds.

    Special care needs to be taken for crc, most FNV1 variants, fletcher, Jenkins. And with GOOD hashes most MUM variants, like mirhash, MUM, wyhash.

    Independently from this, when the attacker knows the seed it will lead to DDOS attacks. Even with crypto hashes in power2 hashtables.

Typical undefined behaviour (UB) problems:

  • Misaligned

    Many word-wise hashes (in opposite to safe byte-wise processing) don't check the input buffer for proper word alignment, which will fail with ubsan or Sparc. word being int32_t or int64_t or even more. On some old RISC hardware this will be a BUS error, you can even let Intel HW generate such a bus error by setting some CPU flag. But generally using misaligned accesses is fine.

    These are: mx3, Spooky, mirhash (but not strict), MUM, fasthash, Murmur3*, Murmur2*, metrohash* (all but cmetro*), Crap8, beamsplitter, lookup3, fletcher4, fletcher2, all sanmayce FNV1a_ variants (FNV1a_YT, FNV1A_Pippip_Yurii, FNV1A_Totenschiff, ...), fibonacci.

    The usual mitigation is to check the buffer alignment either in the caller, provide a pre-processing loop for the misaligned prefix, or copy the whole buffer into a fresh aligned area. Put that extra code inside #ifdef HAVE_ALIGNED_ACCESS_REQUIRED.

  • oob - Out of bounds

    Some hash function assume a padded input buffer which can be accessed past its length up to the word size. This allows for faster loop processing, as no 2nd loop or switch table for the rest is needed, but it requires a cooperative calling enviroment and is as such considered cheating.

  • Signed integer overflow

    A simple type error, this hash needs to use unsigned integer types internally, to avoid undefined and inconsistent behaviour. i.e. SuperFastHash: signed integer overflow: -2147483641 + -113 cannot be represented in type 'int'

  • shift exponent overflow

    With: FNV1A_Pippip_Yurii, FNV1A_Totenschiff, pair_multiply_shift, sumhash32 shift exponent 64 is too large for 64-bit type 'long unsigned int'