chacha20poly1305

README

chacha20poly1305

A chacha20poly1305 implementation, copied from https://git.schwanenlied.me/yawning/chacha20poly1305

Adopted to support the variable tag sizes needed for QUIC.

Documentation

Overview

Package chacha20poly1305 implemnets the RFC 7539 AEAD_CHACHA20_POLY1305 construct. It depends on my ChaCha20 and Poly1305 libraries (and not golang.org/x/crypto for the latter), and attempts to be correct and easy to read over fast.

When the golang.org/x/crypto maintainers feel like providing a sane interface to the Poly1305 code, this will switch to using that, but not before then.

Index

• Constants
• Variables
• type ChaCha20Poly1305
  • func New(key []byte, tagSize uint8) (*ChaCha20Poly1305, error)
  • func (a *ChaCha20Poly1305) NonceSize() int
  • func (a *ChaCha20Poly1305) Open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error)
  • func (a *ChaCha20Poly1305) Overhead() int
  • func (a *ChaCha20Poly1305) Reset()
  • func (a *ChaCha20Poly1305) Seal(dst, nonce, plaintext, additionalData []byte) []byte

Constants

const (
	// KeySize is the key length in bytes (32 bytes, 256 bits).
	KeySize = chacha20.KeySize

	// NonceSize is the nonce (IV) length in bytes (12 bytes, 96 bits).
	NonceSize = chacha20.INonceSize

	// Overhead is the tag length in bytes (16 bytes, 128 bits).
	Overhead = poly1305.Size
)

Variables

var (
	// ErrOpen is the error returned when an Open fails.
	ErrOpen = errors.New("chacha20poly1305: message authentication failed")

	// ErrInvalidTagSize is the error returned when the tag size is > 16
	ErrInvalidTagSize = errors.New("chacha20poly1305: invalid tag size")
)

Types

type ChaCha20Poly1305

type ChaCha20Poly1305 struct {
	// contains filtered or unexported fields
}

ChaCha20Poly1305 is an AEAD_CHACHA20_POLY1305 instance.

func New

func New(key []byte, tagSize uint8) (*ChaCha20Poly1305, error)

New returns a new ChaCha20Poly1305 instance, keyed with a given key.

func (*ChaCha20Poly1305) NonceSize

func (a *ChaCha20Poly1305) NonceSize() int

NonceSize returns the size of the nonce that must be passed to Seal and Open.

func (*ChaCha20Poly1305) Open

func (a *ChaCha20Poly1305) Open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error)

Open decrypts and authenticates ciphertext, authenticates the additional data and, if successful, appends the resulting plaintext to dst, returning the updated slice. The nonce must be NonceSize() bytes long and both it and the additional data must match the value passed to Seal.

Even if the function fails, the contents of dst, up to its capacity, may be overwritten.

func (*ChaCha20Poly1305) Overhead

func (a *ChaCha20Poly1305) Overhead() int

Overhead returns the maximum difference between the lengths of a plaintext and its ciphertext.

func (*ChaCha20Poly1305) Reset

func (a *ChaCha20Poly1305) Reset()

Reset clears all sensitive cryptographic material from a given instance so that it is no longer resident in memory.

func (*ChaCha20Poly1305) Seal

func (a *ChaCha20Poly1305) Seal(dst, nonce, plaintext, additionalData []byte) []byte

Seal encrypts and authenticates plaintext, authenticates the additional data and appends the result to dst, returning the updated slice. The nonce must be NonceSize() bytes long and unique for all time, for a given key.