Data processing apparatus for performing a cryptographic method

A decoding data processing apparatus operable to execute a cryptographic method to form a plaintext sequence of data symbols from an input encrypted ciphertext sequence of data symbols, said cryptographic method comprising a plurality of functional stages, said decoding data processing apparatus comprising:

• a plurality of data processing units arranged to form a pipeline, each of said data processing units being operable to process, in accordance with a respective functional stage of said cryptographic method, an input data quantity to produce a corresponding processed data quantity, said processed data quantity being fed to a subsequent data processing unit in said pipeline;
• and
• a combination element operable to form said plaintext sequence of data symbols based on a combination of said processed data quantities output from a final one of said data processing units of said pipeline and said input encrypted ciphertext sequence of data symbols;
• wherein said data processing apparatus is operable, during an initialisation stage, to supply sequentially to a first one of said data processing units a series of two or more initialisation values as said input data quantities to said pipeline,
• said data processing apparatus being operable to commence a main processing stage, in which said input data quantity to said first data processing unit is formed from an output of said final data processing unit of said pipeline, only after all of said initialisation values have been supplied to said first data processing unit during said initialisation stage.

A decoding data processing apparatus operable to execute a cryptographic method to form a plaintext sequence of data symbols from an input encrypted ciphertext sequence of data symbols, said cryptographic method comprising a plurality of functional stages, said decoding data processing apparatus comprising:

• a plurality of data processing units arranged to form a pipeline, each of said data processing units being operable to process, in accordance with a respective functional stage of said cryptographic method, an input data quantity to produce a corresponding processed data quantity, said processed data quantity being fed to a subsequent data processing unit in said pipeline;
• and
• a combination element operable to form said plaintext sequence of data symbols based on a combination of said processed data quantities output from a final one of said data processing units of said pipeline and said input encrypted ciphertext sequence of data symbols;
• wherein said data processing apparatus is operable, during an initialisation stage, to supply sequentially to a first one of said data processing units a series of two or more initialisation values as said input data quantities to said pipeline,
• said data processing apparatus being operable to commence a main processing stage, in which said input data quantity to said first data processing unit is formed from said input encrypted ciphertext sequence of data symbols, only after all of said initialisation values have been supplied to said first data processing unit during said initialisation stage.

An encoding data processing method operable to execute a cryptographic method to form an encrypted ciphertext sequence of data symbols from an input plaintext sequence of data symbols, said cryptographic method comprising a plurality of functional stages, said encoding data processing method comprising the steps of:

• performing, in series, a plurality of data processing stages, each of said data processing stages comprising the steps of:
• (i) processing, in accordance with a respective functional stage of said cryptographic method, an input data quantity to produce a corresponding processed data quantity;
• and
• (ii) feeding said processed data quantity to a subsequent data processing stage;
• and
• forming said encrypted ciphertext sequence of data symbols based on a combination of said processed data quantities output from a final one of said data processing stages and said input plaintext sequence of data symbols;
• wherein said data processing method comprises:
• an initialisation step for supplying sequentially to a first one of said data processing stages a series of two or more initialisation values as input data quantities;
• and
• a main processing step for forming said input data quantity to said first data processing stage from an output of said final data processing stage, commencing only after all of said initialisation values have been supplied to said first data processing stage during said initialisation step.

A decoding data processing method operable to execute a cryptographic method to form a plaintext sequence of data symbols from an input encrypted ciphertext sequence of data symbols, said cryptographic method comprising a plurality of functional stages, said decoding data processing method comprising the steps of:

• performing, in series, a plurality of data processing stages, each of said data processing stages comprising the steps of:
• (i) processing, in accordance with a respective functional stage of said cryptographic method, an input data quantity to produce a corresponding processed data quantity;
• and
• (ii) feeding said processed data quantity to a subsequent data processing stage;
• and
• forming said plaintext sequence of data symbols based on a combination of said processed data quantities output from a final one of said data processing stages and said input encrypted ciphertext sequence of data symbols;
• wherein said data processing method comprises:
• an initialisation step for supplying sequentially to a first one of said data processing stages a series of two or more initialisation values as input data quantities;
• and
• a main processing step for forming said input data quantity to said first data processing stage from an output of said fmal data processing stage, commencing only after all of said initialisation values have been supplied to said first data processing stage during said initialisation step.

A decoding data processing method operable to execute a cryptographic method to form a plaintext sequence of data symbols from an input encrypted ciphertext sequence of data symbols, said cryptographic method comprising a plurality of functional stages, said decoding data processing method comprising the steps of:

• performing, in series, a plurality of data processing stages, each of said data processing stages comprising the steps of:
• (i) processing, in accordance with a respective functional stage of said cryptographic method, an input data quantity to produce a corresponding processed data quantity;
• and
• (ii) feeding said processed data quantity to a subsequent data processing stage;
• and
• forming said plaintext sequence of data symbols based on a combination of said processed data quantities output from a final one of said data processing stages and said input encrypted ciphertext sequence of data symbols;
• wherein said data processing method comprises:
• an initialisation step for supplying sequentially to a first one of said data processing stages a series of two or more initialisation values as input data quantities;
• and
• a main processing step for forming said input data quantity to said first data processing unit from said input encrypted ciphertext sequence of data symbols, commencing only after all of said initialisation values have been supplied to said first data processing stage during said initialisation step.

A signal comprising an encrypted ciphertext sequence of data symbols, said encrypted ciphertext sequence of data symbols having been produced according to an encoding data processing method operable to execute a cryptographic method to form said encrypted ciphertext sequence of data symbols from an input plaintext sequence of data symbols, said cryptographic method comprising a plurality of functional stages, said encoding data processing method comprising the steps of:

• performing, in series, a plurality of data processing stages, each of said data processing stages comprising the steps of:
• (i) processing, in accordance with a respective functional stage of said cryptographic method, an input data quantity to produce a corresponding processed data quantity;
• and
• (ii) feeding said processed data quantity to a subsequent data processing stage;
• and
• forming said encrypted ciphertext sequence of data symbols based on a combination of said processed data quantities output from a final one of said data processing stages and said input plaintext sequence of data symbols;
• wherein said data processing method comprises:
• an initialisation step for supplying sequentially to a first one of said data processing stages a series of two or more initialisation values as input data quantities;
• a main processing step for forming said input data quantity to said first data processing stage from an output of said final data processing stage, commencing only after all of said initialisation values have been supplied to said first data processing stage during said initialisation step;
• and
• a sub-key generation stage preceding said initialisation stage for generating, for each of a plurality of master-key values and in accordance with a sub-key value generation method of said cryptographic method, at least one sub-key value, each of said generated sub-key values being supplied to a corresponding data processing stage, each of said data processing stages being operable to use a supplied sub-key value in accordance with said respective functional stage of said cryptographic method;
• and
• wherein, for each initialisation value, there is a corresponding master-key value, each of said data processing stages operable to use a supplied sub-key value being operable to use a supplied sub-key value generated from said master-key value corresponding to said initialisation value from which said data quantity currently being processed by said data processing stage has been generated.