Product block cipher system for data security

A device for performing a product block cipher operation on a block of data bits under control of a set of cipher key bits comprising:

• first store means storing said block of data bits,
• first linear transformation means permuting said set of cipher key bits,
• said permuted cipher key bits being grouped into a plurality of permuted cipher key bit segments,
• means connected to said first store means duplicating predetermined ones of the data bits of said block of data bits to produce an expanded block of data bits equal in number to the number of said permuted cipher key bits,
• said expanded block of data bits being grouped into a plurality of data bit segments equal in number to said plurality of permuted cipher key bit segments,
• a plurality of substitution transformation means responsive to said plurality of data bit segments and said plurality of permuted cipher key bit segments carrying out different substitution transformation functions to produce a substitution set of bits equal in number to the number of bits in said block of data bits, and
• second linear transformation means connected to said plurality of substitution transformation means permuting said substitution set of bits whereby the combined transformation results in a product block cipher of said block of data bits.

A device for performing a product block cipher operation on a block of 32 data bits under control of a set of 48 cipher key bits comprising:

• first store means storing said block of 32 data bits,
• first linear transformation means permuting said set of 48 cipher key bits,
• means connected to said first store means duplicating 16 predetermined ones of the data bits of said block of 32 data bits to produce an expanded block containing 48 data bits,
• means connected to said expansion means and said first linear transformation means carrying out a many to one substitution transformation function in accordance with said expanded block of 48 data bits and said 48 permuted cipher key bits to produce a substitution set of 32 bits, and
• second linear transformation means connected to said substitution transformation means permuting said substitution set of 32 bits, whereby the combined transformation results in a product block cipher of said block of 32 data bits.

A process for product block ciphering a block of data represented by a combination of binary digits under control of a cipher key represented by a combination of binary digits comprising the steps of:

• a. storing said block of data bits in a first store means,
• b. linearly transforming said cipher key by rearranging a portion of said cipher key combination of binary digits,
• c. duplicating predetermined ones of the data bits of said block of data bits to provide an expanded block of data bits consisting of said duplicated data bits and said block of data bits,
• said expanded block of data bits being equal in number to the number of said transformed cipher key bits,
• d. carrying out a substitution transformation function in accordance with said expanded block of data bits and said transformed cipher key bits to produce a substitution set of bits represented by a combination of binary digits equal in number to the number of bits in said block of data, and
• e. linearly transforming said substitution set of bits by rearranging said substitution combination of binary digits,
• whereby the combined transformation results in a product block cipher of said block of data bits.

A process for product block ciphering a block of data bits under control of a set of cipher key bits comprising the steps of:

• a. storing said block of data bits in a first store means,
• b. linearly transforming said set of cipher key bits into a plurality of transformed cipher key bit segments,
• c. duplicating predetermined ones of the data bits of said block of data bits to provide an expanded block of data bits consisting of said duplicated data bits and said block of data bits grouped into a plurality of data bit segments equal in number to said plurality of transformed cipher key bit segments,
• d. carrying out a plurality of different substitution transformation functions in accordance with said plurality of data bit segments and said plurality of transformed cipher key segments to produce a substitution set of bits equal in number to the number of bits in said block of data bits, and
• e. linearly transforming said substitution set of bits,
• whereby the combined transformation results in a product block cipher of said block of data bits.