Nope, none of the amateur bands allow encryption. There are “unlicensed” (technically licensed-by-rule) bands that do. Typically the ISM bands, which is what W

Nope, none of the amateur bands allow encryption. There are “unlicensed” (technically licensed-by-rule) bands that do. Typically the ISM bands, which is what WiFi uses. But they aren't as open for experimental use as the amateur bands. (But yes, even on amateur bands a digital signature would be fine. You just can't obscure the meaning of the message.)