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add random GF(2^127)-element generator

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Evgenii 2019-01-29 14:25:17 +03:00
parent b380bca1d2
commit ebb124e812
2 changed files with 26 additions and 6 deletions
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7
gf127/gf127.go
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@ -12,6 +12,7 @@ import (
"encoding/hex"
"errors"
"math/bits"
"math/rand"
)
// GF127 represents element of GF(2^127)
@ -36,6 +37,12 @@ func New(lo, hi uint64) *GF127 {
return &GF127{lo, hi}
}
// Random returns random element from GF(2^127).
// Is used mostly for testing.
func Random() *GF127 {
return &GF127{rand.Uint64(), rand.Uint64() >> 1}
}
// String returns hex-encoded representation, starting with MSB.
func (c *GF127) String() string {
return hex.EncodeToString(c.ByteArray())

25
gf127/gf127_test.go
View file

@ -1,17 +1,18 @@
package gf127
import (
"math/rand"
"testing"
)
const maxUint64 = ^uint64(0)
func TestAdd(t *testing.T) {
a := &GF127{rand.Uint64(), rand.Uint64() >> 1}
b := &GF127{rand.Uint64(), rand.Uint64() >> 1}
e := &GF127{a[0] ^ b[0], a[1] ^ b[1]}
c := &GF127{0, 0}
var (
a = Random()
b = Random()
e = &GF127{a[0] ^ b[0], a[1] ^ b[1]}
c = new(GF127)
)
c.Add(a, b)
if e[0] != c[0] || e[1] != c[1] {
t.Errorf("expected (%s), got (%s)", e.String(), c.String())
@ -74,10 +75,22 @@ var testCasesInv = [][2]*GF127{
}
func TestInv(t *testing.T) {
c := new(GF127)
var a, b, c = new(GF127), new(GF127), new(GF127)
for _, tc := range testCasesInv {
if Inv(tc[0], c); !c.Equals(tc[1]) {
t.Errorf("expected (%s), got (%s)", tc[1].String(), c.String())
}
}
for i := 0; i < 3; i++ {
// 0 has no inverse
if a = Random(); a.Equals(&GF127{0, 0}) {
continue
}
Inv(a, b)
Mul(a, b, c)
if !c.Equals(&GF127{1, 0}) {
t.Errorf("expected inverse of (%s), got (%s)", a.String(), b.String())
}
}
}