Good Morning.
if you use https as the transport it is encrypted on the wire.
If you want to encrypt the data specifically, looks like android has the javax.crypto library included. I have seen some examples on the net using AES encryption.
Here is one such link
However the device may need to know the passwords to decrypt it unless you are using a public/private keys and you hold the public key. But then it only gives you the authentication or certification of what is sent.
Thanks
Satya