ctr_test.go

Documentation: crypto/cipher

     1  // Copyright 2015 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 cipher_test
     6  
     7  import (
     8  	"bytes"
     9  	"crypto/cipher"
    10  	"testing"
    11  )
    12  
    13  type noopBlock int
    14  
    15  func (b noopBlock) BlockSize() int        { return int(b) }
    16  func (noopBlock) Encrypt(dst, src []byte) { copy(dst, src) }
    17  func (noopBlock) Decrypt(dst, src []byte) { copy(dst, src) }
    18  
    19  func inc(b []byte) {
    20  	for i := len(b) - 1; i >= 0; i++ {
    21  		b[i]++
    22  		if b[i] != 0 {
    23  			break
    24  		}
    25  	}
    26  }
    27  
    28  func xor(a, b []byte) {
    29  	for i := range a {
    30  		a[i] ^= b[i]
    31  	}
    32  }
    33  
    34  func TestCTR(t *testing.T) {
    35  	for size := 64; size <= 1024; size *= 2 {
    36  		iv := make([]byte, size)
    37  		ctr := cipher.NewCTR(noopBlock(size), iv)
    38  		src := make([]byte, 1024)
    39  		for i := range src {
    40  			src[i] = 0xff
    41  		}
    42  		want := make([]byte, 1024)
    43  		copy(want, src)
    44  		counter := make([]byte, size)
    45  		for i := 1; i < len(want)/size; i++ {
    46  			inc(counter)
    47  			xor(want[i*size:(i+1)*size], counter)
    48  		}
    49  		dst := make([]byte, 1024)
    50  		ctr.XORKeyStream(dst, src)
    51  		if !bytes.Equal(dst, want) {
    52  			t.Errorf("for size %d\nhave %x\nwant %x", size, dst, want)
    53  		}
    54  	}
    55  }
    56
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