On Fri, Feb 8, 2019 at 7:42 PM Michael Jones <[email protected]> wrote:
> clustering:
> https://www.cs.cornell.edu/courses/cs3110/2014fa/lectures/13/lec13.html
>
> careful hash functions often treat short inputs specially.
>
> iterated shift-xor alone is weak in expanding the "changed bits(s)" signal,
> at least by comparison to a) large prime multiply, b) good s-boxes, c)
> introduction of keyed material.
Hm, thanks. I would like to try a particular version of this prime
multiplication idea wih utf8 strings.
I wrote for loops to find collisions (attached). It takes 3 seconds
and finds no collision for strings with length < 4.
The next step (including length=4, commented in the code) will take
13+ min and 32+ gb ram, so I appreciate if anyone with sufficient RAM
could try that and report the result ;P
Thanks..
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
package main
import "fmt"
func Txt2int(s string) uint64 {
x := uint64(len(s))
for i := len(s) - 1; i >= 0; i-- {
x *= 11400714819323198549
x += uint64(s[i])
}
return x
}
const N = 16646656 // 4244897281
var mp = make(map[uint64]bool, N)
var bf = []byte("abcd")
func main() {
mp[0] = true
for i := 255; i > 0; i-- {
bf[0] = byte(i)
mp[Txt2int(string(bf[:1]))] = true
for k := 255; k > 0; k-- {
bf[1] = byte(k)
mp[Txt2int(string(bf[:2]))] = true
for r := 255; r > 0; r-- {
bf[2] = byte(r)
mp[Txt2int(string(bf[:3]))] = true
/* for s := 255; s > 0; s-- {
bf[3] = byte(s)
mp[Txt2int(string(bf[:4]))] = true
} */
}
}
}
fmt.Println(N - len(mp))
}
