A sender device includes: a first sequence generator configured to generate a first sequence of bits having a bit pattern that incudes first bit values and second bit values; a first parsing processor configured to receive a first plurality of data blocks and the first sequence of bits, and select a first subset of data blocks and a second subset of data blocks from the first plurality of data blocks based on the bit pattern; an encryption processor configured to encrypt the selected first subset of data blocks received from the first parsing processor to generate encrypted data blocks and output the encrypted data blocks to an output terminal that is configured to output the encrypted data blocks and the selected second subset of data blocks as unencrypted data blocks from the sender device.