cryptoutils

README

go-cryptoutils

Go crypto utils.

Install

go get github.com/koofr/go-cryptoutils

Testing

go get -t
go test

Documentation

Index

• type BetterCTR
  • func NewBetterCTR(block cipher.Block, iv []byte) *BetterCTR
  • func NewBetterCTRFromState(block cipher.Block, state []byte) *BetterCTR
  • func (x *BetterCTR) GetState() []byte
  • func (x *BetterCTR) SetState(state []byte) error
  • func (x *BetterCTR) XORKeyStream(dst, src []byte)

Examples

• NewBetterCTR

Types

type BetterCTR

type BetterCTR struct {
	// contains filtered or unexported fields
}

func NewBetterCTR

func NewBetterCTR(block cipher.Block, iv []byte) *BetterCTR

NewBetterCTR returns a Stream which encrypts/decrypts using the given Block in counter mode. The length of iv must be the same as the Block's block size.

Example

key := []byte("example key 1234")
plaintext := []byte("some plaintext")

block, err := aes.NewCipher(key)
if err != nil {
	panic(err)
}

// The IV needs to be unique, but not secure. Therefore it's common to
// include it at the beginning of the ciphertext.
ciphertext := make([]byte, aes.BlockSize+len(plaintext))
iv := ciphertext[:aes.BlockSize]
if _, err := io.ReadFull(rand.Reader, iv); err != nil {
	panic(err)
}

stream := cryptoutils.NewBetterCTR(block, iv)
stream.XORKeyStream(ciphertext[aes.BlockSize:aes.BlockSize+4], plaintext[:4])

state := stream.GetState()

anotherStream := cryptoutils.NewBetterCTRFromState(block, state)
anotherStream.XORKeyStream(ciphertext[aes.BlockSize+4:], plaintext[4:])

// It's important to remember that ciphertexts must be authenticated
// (i.e. by using crypto/hmac) as well as being encrypted in order to
// be secure.

// CTR mode is the same for both encryption and decryption, so we can
// also decrypt that ciphertext with NewBetterCTR.

plaintext2 := make([]byte, len(plaintext))
stream = cryptoutils.NewBetterCTR(block, iv)
stream.XORKeyStream(plaintext2, ciphertext[aes.BlockSize:])

fmt.Printf("%s\n", plaintext2)

Output:

some plaintext

func NewBetterCTRFromState

func NewBetterCTRFromState(block cipher.Block, state []byte) *BetterCTR

NewBetterCTR returns a Stream from state

func (*BetterCTR) GetState

func (x *BetterCTR) GetState() []byte

func (*BetterCTR) SetState

func (x *BetterCTR) SetState(state []byte) error

func (*BetterCTR) XORKeyStream

func (x *BetterCTR) XORKeyStream(dst, src []byte)