Carlos Serrão Antonio Serra Miguel Sales Dias Jaime Delgado Protection of MP3 Music Files Using Digital Rights Management and Symmetric Ciphering. 128-135 2006 conf/axmedis/2006 AXMEDIS http://doi.ieeecomputersociety.org/10.1109/AXMEDIS.2006.42 db/conf/axmedis/axmedis2006.html#SerraoSDD06