US Patent 8259934 Methods and devices for a chained encryption mode

An encryption chaining mode takes plaintext block N, generates encryption key N by combining, preferably by XOR, encryption key N-1 and plaintext block N-1 and encrypts plaintext block N using an encryption algorithm with encryption key N to output ciphertext block N. Encryption key for the first plaitnext block is generated by XOR-ing a random Initialization vector and a random intialization key K. In a preferred embodiment, initialization key K is subkeys resulting form a key schedule algorithm and encryption key N-1 is only one of the subkeys. Encryption key for the first plaintext block is generated by XOR-ing a random Initialization vector and one subkey resulting form a key schedule algorithm. Also provided is a corresponding decryption method, an encryption device, a decryption device.