Constant-time comparison of two bytes/0 (16) byte secrets, such as authentication tags, whose timing does not depend on where they differ.

Returns 0 when the binaries are equal and -1 otherwise. Both arguments must be exactly bytes/0 bytes long.

Tag = libsodium_randombytes:buf(libsodium_crypto_verify_16:bytes()),
0 = libsodium_crypto_verify_16:crypto_verify_16(Tag, Tag),
<<First, Rest/binary>> = Tag,
-1 = libsodium_crypto_verify_16:crypto_verify_16(Tag, <<(First bxor 1), Rest/binary>>).