github.com/code-reading/golang@v0.0.0-20220303082512-ba5bc0e589a3/go/src/crypto/elliptic/internal/fiat/p521_test.go (about)

     1  // Copyright 2021 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package fiat_test
     6  
     7  import (
     8  	"crypto/elliptic/internal/fiat"
     9  	"crypto/rand"
    10  	"testing"
    11  )
    12  
    13  func p521Random(t *testing.T) *fiat.P521Element {
    14  	buf := make([]byte, 66)
    15  	if _, err := rand.Read(buf); err != nil {
    16  		t.Fatal(err)
    17  	}
    18  	buf[65] &= 1
    19  	e, err := new(fiat.P521Element).SetBytes(buf)
    20  	if err != nil {
    21  		t.Fatal(err)
    22  	}
    23  	return e
    24  }
    25  
    26  func TestP521Invert(t *testing.T) {
    27  	a := p521Random(t)
    28  	inv := new(fiat.P521Element).Invert(a)
    29  	one := new(fiat.P521Element).Mul(a, inv)
    30  	if new(fiat.P521Element).One().Equal(one) != 1 {
    31  		t.Errorf("a * 1/a != 1; got %x for %x", one.Bytes(), a.Bytes())
    32  	}
    33  	inv.Invert(new(fiat.P521Element))
    34  	if new(fiat.P521Element).Equal(inv) != 1 {
    35  		t.Errorf("1/0 != 0; got %x", inv.Bytes())
    36  	}
    37  }