Block Data Encryption Using Random Number Encoding

The patent applies preliminary action by pre-computing and storing multiple possible previous ciphertext blocks (c_i-j) that could be used for decoding the current block. Instead of requiring the immediate previous block c_{i-1}, the system prepares a set of alternative previous blocks in advance, allowing the receiver to decode using any available block from the set, thus resolving the contradiction between security and ease of operation.

The patent changes the parameter from requiring a single specific previous block (c_{i-1}) to accepting multiple possible previous blocks (c_{i-j} where j is in a predefined set). This parameter change allows the decryption process to be more flexible and resilient to packet loss, maintaining both security and operational ease.

The patent makes the system adaptable to multicast protocols by pre-computing multiple alternative previous ciphertext blocks that can be embedded in the transmitted data stream. This allows receivers in a multicast group to decode data using any available previous block, accommodating the unreliable nature of multicast networks while maintaining CBC-mode security.

The patent enhances universality by making the decryption process work with multiple different previous blocks rather than requiring a specific one. This multi-functionality allows the same encryption scheme to work reliably in both unicast and multicast environments, as well as in networks with varying levels of reliability.