The message must be encrypted using one-time pad like scheme.

When you send him a message encrypted using the day's pad, he can decipher it.

The data in those packets is encrypted using the permanent keys.

Master password is encrypted under Blowfish using a fixed key.

For added security, however, each individual message was encrypted using an additional key modification.

The message had been encrypted using her public key.

By limiting the number of messages encrypted using a single key, those attacks are made more difficult.

Each message has to be encrypted using some cryptographic key that is known only to the intended receivers.

And as we remember, the way this functions is something can be encrypted using their publicly available key which everyone can know.

The data is encrypted using a pair of session keys chosen for just that message.