kubernetes/vendor/golang.org/x/crypto/nacl/secretbox/secretbox.go

const Overhead …

// setup produces a sub-key and Salsa20 counter given a nonce and key.
func setup(subKey *[32]byte, counter *[16]byte, nonce *[24]byte, key *[32]byte) { … }

// sliceForAppend takes a slice and a requested number of bytes. It returns a
// slice with the contents of the given slice followed by that many bytes and a
// second slice that aliases into it and contains only the extra bytes. If the
// original slice has sufficient capacity then no allocation is performed.
func sliceForAppend(in []byte, n int) (head, tail []byte) { … }

// Seal appends an encrypted and authenticated copy of message to out, which
// must not overlap message. The key and nonce pair must be unique for each
// distinct message and the output will be Overhead bytes longer than message.
func Seal(out, message []byte, nonce *[24]byte, key *[32]byte) []byte { … }

// Open authenticates and decrypts a box produced by Seal and appends the
// message to out, which must not overlap box. The output will be Overhead
// bytes smaller than box.
func Open(out, box []byte, nonce *[24]byte, key *[32]byte) ([]byte, bool) { … }