Patent ID: 6950517

Claim:
A method for encrypting and authenticating data as a single entity, comprising: arranging data into a plurality of plaintext blocks, each sized according to a cipher block size; specifying at least one cleartext position for which at least one ciphertext block will be the same as a corresponding plaintext block; determining a plurality of noise blocks using a nonce value and a first key; determining a plurality of intermediate ciphertext blocks, wherein the first intermediate ciphertext block corresponds to an encrypted nonce value, and the remaining intermediate ciphertexts are computed iteratively by encrypting a plurality of intermediate plaintext blocks with a second key, wherein each intermediate plaintext block is a combination of one of the plurality of plaintext blocks and a preceding intermediate ciphertext block; determining a plurality of ciphertext blocks by using the plurality of intermediate ciphertext blocks and the plurality of noise blocks, wherein the first ciphertext block is the same as the first intermediate ciphertext block and the remaining ciphertext blocks are derived by combining a corresponding intermediate ciphertext block with a corresponding noise block; computing an input checksum value based on the plurality of plaintext blocks and the intermediate ciphertext block corresponding to the last plaintext block; computing an output checksum value based on the plurality of ciphertext blocks and a noise block; computing an authentication tag by encrypting the input checksum value with the second key and combining the encrypted input checksum value with the output checksum; substituting each of the plurality of ciphertext blocks that is specified by a cleartext position with a corresponding plaintext block; and appending the authentication tag.