//go:noescape
func gcmAesEnc(productTable *[256]byte, dst, src []byte, ctr, T *[16]byte, ks []uint32)

//go:noescape
func gcmAesDec(productTable *[256]byte, dst, src []byte, ctr, T *[16]byte, ks []uint32)

//go:noescape
func gcmAesFinish(productTable *[256]byte, tagMask, T *[16]byte, pLen, dLen uint64)

const (
	gcmBlockSize         = 16
	gcmTagSize           = 16
	gcmMinimumTagSize    = 12 // NIST SP 800-38D recommends tags with 12 or more bytes.