def encrypt_and_pack(plaintext: bytes, ring: Keyring, privkey: bytes) -> str:
symm_ciphertext, symm_key = _symmetric_encrypt(plaintext)
group_keys = ring.encrypt(symm_key)
fmt, ciphertext_block = pack_keys_and_ciphertext(group_keys, symm_ciphertext)
sig = asymmetric.sign(ciphertext_block, privkey)
fmt, packed = pack_sig_and_block(fmt, sig, ciphertext_block)
string_data_to_write = serialize_everything(fmt, packed)
return string_data_to_write
