Message authentication code with improved error tolerance

A method of generating a message authentication code (MAC) associated with an image comprising the steps of:

• receiving a plurality of blocks of image coefficient data including a respective DC coefficient, each coefficient having an original value from a range of values wherein said plurality of blocks are arranged in rows and columns corresponding to said image;
• defining an error tolerance buffer by dividing said range of values into first and second regions having allowed coefficient values and a buffer region therebetween having disallowed coefficient values;
• linearly mapping said original values of said DC coefficients with most significant bits (MSB) of zero to modified values included in said first region;
• linearly mapping said original values of said DC coefficients with MSBs of one to modified values included in said second region;
• generating a row representation for each row of said blocks based on the number of said modified values that map into said second region;
• generating a column representation for each column of said blocks based on the number of said modified values that map into said second region;
• and
• generating a MAC according to a predetermined strategy using said row and column representations.

A system for generating a message authentication code (MAC) associated with an image comprising:

• means for receiving a plurality of blocks of image coefficient data, each coefficient having an original value from a range of values;
• means for defining an error tolerance buffer by dividing said range of values into first and second regions having allowed coefficient values and a buffer region therebetween having disallowed coefficient values;
• means for mapping an original value of at least one coefficient from each block of image coefficient data to a modified value included in one of said first and second regions;
• and
• means for generating a MAC according to a predetermined strategy as a function of a respective most significant bit (MSB) of said modified image coefficient values.