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package chacha20poly1305

import ""

Package chacha20poly1305 implements the ChaCha20-Poly1305 AEAD and its extended nonce variant XChaCha20-Poly1305, as specified in RFC 8439 and draft-irtf-cfrg-xchacha-01.



Package Files

chacha20poly1305.go chacha20poly1305_amd64.go chacha20poly1305_generic.go xchacha20poly1305.go


const (
    // KeySize is the size of the key used by this AEAD, in bytes.
    KeySize = 32

    // NonceSize is the size of the nonce used with the standard variant of this
    // AEAD, in bytes.
    // Note that this is too short to be safely generated at random if the same
    // key is reused more than 2³² times.
    NonceSize = 12

    // NonceSizeX is the size of the nonce used with the XChaCha20-Poly1305
    // variant of this AEAD, in bytes.
    NonceSizeX = 24

func New Uses

func New(key []byte) (cipher.AEAD, error)

New returns a ChaCha20-Poly1305 AEAD that uses the given 256-bit key.

func NewX Uses

func NewX(key []byte) (cipher.AEAD, error)

NewX returns a XChaCha20-Poly1305 AEAD that uses the given 256-bit key.

XChaCha20-Poly1305 is a ChaCha20-Poly1305 variant that takes a longer nonce, suitable to be generated randomly without risk of collisions. It should be preferred when nonce uniqueness cannot be trivially ensured, or whenever nonces are randomly generated.


aead, err := NewX(key)
if err != nil {
    log.Fatalln("Failed to instantiate XChaCha20-Poly1305:", err)

for _, msg := range []string{
    "Attack at dawn.",
    "The eagle has landed.",
    "Gophers, gophers, gophers everywhere!",
} {
    // Encryption.
    nonce := make([]byte, NonceSizeX)
    if _, err := cryptorand.Read(nonce); err != nil {
    ciphertext := aead.Seal(nil, nonce, []byte(msg), nil)

    // Decryption.
    plaintext, err := aead.Open(nil, nonce, ciphertext, nil)
    if err != nil {
        log.Fatalln("Failed to decrypt or authenticate message:", err)

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


Attack at dawn.
The eagle has landed.
Gophers, gophers, gophers everywhere!

Package chacha20poly1305 imports 7 packages (graph) and is imported by 266 packages. Updated 2020-01-18. Refresh now. Tools for package owners.