+ *
+ * The @salsa20_naclbox@ with a 192-bit nonce is exactly the scheme
+ * implemented in Bernstein's `NaCl' library as @crypto_secretbox@, except
+ * that it's flexible regarding tag placement rather than insisting on
+ * prefixing it to the ciphertext. Unlike NaCl, we provide a restartable
+ * interface, and allow the use of other ciphers and nonce lengths.