Strong, fast, simple, non-cryptography hash function
public static int mzHash32(final byte[] data, int start, int length, int seed) {
int hash = 0x95DE1432 ^ seed;
for(int i = 0; i < length; i++)
hash = (0xA8657C5B * (i + data[start + i])) ^ (hash << 2) ^ (hash >>> 2);
return hash;
}It has an absolutely uniform, chaotic distribution of hash values independent of the number, length and type of input values.
It also has a good Avalanche Effect property: even a minimal differences (1 bit) of input values produces very different hash values.
Hash funtion: java.lang.String.hashCode()
Source file: words_en.txt
Distinct words: 65503
Collisions: 118 (expected 0.4994)
Monte Carlo Pi: 3.251076 (error 3.48%)
Hash funtion: mzHash32()
Source file: words_en.txt
Distinct words: 65503
Collisions: 0 (expected 0.4994)
Monte Carlo Pi: 3.142346 (error 0.02%)
mzHash32 produces a very low number of collisions for each reasonably large number of distinct values; it is close to the collisions number of a Universal Hash Function.
The number is given by the formula n-m*(1-((m-1)/m)^n) where n is the number of input values, m is the number of all possible hash values (2^32 or 2^64).
| Data input | #Vaues | #Expected Collisions | mzHash | Murmur3 | XX |
|---|---|---|---|---|---|
| File words_en.txt | 65,503 | 0 | 0 | 0 | 0 |
| File words_es.txt | 74,571 | 1 | 0 | 2 | 0 |
| File words_latin.txt | 80,007 | 1 | 1 | 1 | 1 |
| File words_it.txt | 117,558 | 2 | 0 | 0 | 2 |
| File words_en_es_it_latin.txt | 315,198 | 12 | 9 | 9 | 9 |
| File words_and_numbers.txt | 429,187 | 21 | 17 | 20 | 19 |
| File first_million_primes.txt | 1,000,000 | 116 | 109 | 118 | 85 |
| File random_64_signed_nums.txt | 1,000,000 | 116 | 105 | 110 | 143 |
| Numbers in english from "zero" to "nine million nine hundred ninety-nine thousand nine hundred ninety-nine" | 10,000,000 | 11,633 | 11,735 | 11,672 | 11,474 |
| File rockyou.txt dictionary of common passwords | 14,442,069 | 24,254 | 168,561 | 168,887 | 168,563 |
| Numbers in english from "five hundred thirty-nine billion three hundred twenty million seven hundred one thousand four hundred eighty-three" to "five hundred thirty-nine billion four hundred twenty million seven hundred one thousand four hundred eighty-two" | 100,000,000 | 1,155,171 | 1,152,258 | 1,155,029 | 1,154,135 |
| Number as strings from "1234567890123456789" to "1234567890223456788" |
100,000,000 | 1,155,171 | 1,154,640 | 1,155,789 | 808,693 |
| Strings from "abcdefg1234567890 123456789hijklmn" to "abcdefg1234567890 223456788hijklmn" |
100,000,000 | 1,155,171 | 1,125,889 | 1,152,600 | 1,037,151 |
| Numbers as strings from "0" to "999999999" | 1,000,000,000 | 107,882,641 | 107,105,249 | 107,822,463 | 110,287,893 |
| Numbers as strings from "aaaa0aaaa" to "aaaa1999999999aaaa" | 2,000,000,000 | 401,068,994 | 400,972,197 | 401,043,716 | 391,119,332 |
| Hex numbers as string from "0" to "7FFFFFFE" | 2,147,483,647 | 457,545,699 | 457,447,653 | 457,465,265 | 460,825,702 |
| Data input | #Vaues | #Expected Collisions | mzHash | Murmur3 | XX |
|---|---|---|---|---|---|
| Binary 32 bytes random | 100,000 | 1 | 1 | 0 | 2 |
| Binary 40 bytes [b,b,b,b,b,b,b,b,b,b] b from FF676980 to FFFFFFFF | 10,000,000 | 11,633 | 11,295 | 11,695 | 11,846 |
| Binary 24 bytes [b,b,b,b,b,b], b from 00000000 to 05F5E0FF | 100,000,000 | 1,155,171 | 1,155,140 | 1,154,653 | 1,411,483 |
| Binary 24 bytes [b,b*3,b*5,b*7,b*11,b*13], b from 00000000 to 05F5E0FF | 100,000,000 | 1,155,171 | 1,154,633 | 1,154,542 | 1,160,003 |
| Binary 24 bytes [b,b,b,b,b,b], b from 00000000 to 05F5E0FF | 1,000,000,000 | 107,882,641 | 107,908,082 | 107,880,319 | 113,834,210 |
MzHash32, like most non-cryptographic functions, is non-secure because it is not specifically designed to be difficult to reverse by an adversary, making it unsuitable for cryptographic purposes. Its use is instead recommended in all other contexts where hash functions are used.
Like other non-cryptographic functions, its security depends on the secrecy of the possibly used seed.
It is minimalist, elegant, straightforward and can be easily written in virtually any programming language. It produces the same result with x86 and x64 (or different) platforms. Currently C and Java versions are available.
MzHash32 demonstrates to have an excellet quality of the dispersion, close to an ideal Universal Hash Function. It is simple, portable and produces same results in all platform (x86 and x64). On the other hand it is slower than XX and Murmur3. If the goal is the quality of the dispersion and have the same result on x86 and x64 platforms, mzHash32 is certainly the function to choose!