Patent ID: 8594330

Claim:
A whitebox descrambler for descrambling a ciphertext to obtain a cleartext message, wherein the descrambler is executed in a computer processor and is configured to implement operations including: receiving a personalized transformed key from an external preprocessing module, the personalized transformed key comprising preprocessed data as a result of applying a first part of a descrambling operation in the external preprocessing module; receiving the input ciphertext; generating an output data by applying a second part of the descrambling operation to the input ciphertext using the personalized transformed key as an input to the second part of the descrambling operation, including: splitting the personalized transformed key in a predefined number of transformed key parts of equal bit length; for each transformed key part, receiving, in a block cipher round module, an input ciphertext data and selecting, from a lookup table, an output at a location indicated by a first bit pattern of the input ciphertext data and a second bit pattern based on the transformed key part; and applying an inverse transformation to the personalized transformed key before generating the output data.