Method and apparatus for advanced byte-oriented symmetric key block cipher with variable length key and block

A system for providing a byte-oriented symmetric key block cipher which supports a variable length symmetric input key, a variable length block, and a variable number of rounds, comprising:

• means for determining a number of rounds of cipher processing to use as said variable number of rounds, a key length of said variable length symmetric input key, and a block length of said variable length block;
• means for generating a plurality of sub-keys using said symmetric input key as an input value, wherein each of said generated sub-keys is equal in length to said block length and where a distinct one of said sub-keys is generated for each of said number of rounds;
• means for obtaining an input data block to be encrypted, wherein said input data block comprises a plurality of input data bytes, said plurality being equal in number to said block length;
• and
• means for iteratively performing a set of round functions a number of times equal to said number of rounds in order to encrypt said input data block, wherein said set of round functions comprises a mixing function, a permuting function, and a key-dependent substitution function, and wherein said means for iteratively performing further comprises:
• means for performing said mixing function by mixing each of said input data bytes using a first XOR operation and a second XOR operation, wherein said first and second XOR operations are different, followed by a first substitution-box (S-box) lookup operation, thereby creating a plurality of mixed bytes;
• means for performing said permuting function by swapping each of said mixed bytes, thereby creating a plurality of permuted bytes;
• means for performing said key-dependent substitution function by substituting a byte value for each of said permuted bytes, wherein said byte value is determined by performing a third XOR operation followed by a second S-box lookup operation, thereby creating a plurality of substituted bytes;
• and
• means for treating said plurality of substituted bytes as said plurality of input data bytes for a subsequent iteration of said means for iteratively performing, provided said number of times has not been reached.

A method of providing a byte-oriented symmetric key block cipher which supports a variable length symmetric input key, a variable length block, and a variable number of rounds, comprising the steps of:

• determining a number of rounds of cipher processing to use as said variable number of rounds, a key length of said variable length symmetric input key, and a block length of said variable length block;
• generating a plurality of sub-keys using said symmetric input key as an input value, wherein each of said generated sub-keys is equal in length to said block length and where a distinct one of said sub-keys is generated for each of said number of rounds;
• obtaining an input data block to be encrypted, wherein said input data block comprises a plurality of input data bytes, said plurality being equal in number to said block length;
• and
• iteratively performing a set of round functions a number of times equal to said number of rounds in order to encrypt said input data block, wherein said set of round functions comprises a mixing function, a permuting function, and a key-dependent substitution function, and wherein said iteratively performing step further comprises the steps of:
• performing said mixing function by mixing each of said input data bytes using a first XOR operation and a second XOR operation, wherein said first and second XOR operations are different, followed by a first substitution-box (S-box) lookup operation, thereby creating a plurality of mixed bytes;
• performing said permuting function by swapping each of said mixed bytes, thereby creating a plurality of permuted bytes;
• performing said key-dependent substitution function by substituting a byte value for each of said permuted bytes, wherein said byte value is determined by performing a third XOR operation followed by a second S-box lookup operation, thereby creating a plurality of substituted bytes;
• and
• treating said plurality of substituted bytes as said plurality of input data bytes for a subsequent iteration of said iteratively performing step, provided said number of times has not been reached.