US 7,545,938 B2
	Digital watermarking which allows tampering to be detected on a block-specific basis
Yasuyuki Nomizu, Kanagawa (Japan); Takanori Yano, Kanagawa (Japan); Junichi Hara, Kanagawa (Japan); Hiroyuki Sakuyama, Tokyo (Japan); Taku Kodama, Kanagawa (Japan); Yasuyuki Shinkai, Kanagawa (Japan); Toshio Miyazawa, Kanagawa (Japan); Nekka Matsuura, Kanagawa (Japan); and Takayuki Nishimura, Tottori (Japan)
Assigned to Ricoh Company Ltd., Tokyo (Japan)
Filed on Nov. 10, 2003, as Appl. No. 10/703,509.
Claims priority of application No. 2002-326544 (JP), filed on Nov. 11, 2002.
Prior Publication US 2005/0053239 A1, Mar. 10, 2005
Int. Cl. H04N 7/167 (2006.01); G06F 11/30 (2006.01); H04L 9/00 (2006.01)

U.S. Cl. 380—220  [380/201; 380/202; 380/269; 713/167; 713/176; 713/181; 713/194; 726/1; 726/26; 726/32]

47 Claims

1. An apparatus for generating codes, comprising: a processor configured to control operation of respective units of the apparatus; a quantization unit which generates quantization coefficients by performing a discrete wavelet transform with respect to each of tiles into which an image is divided; a block division unit which divides the quantization coefficients into blocks; a hash conversion unit which performs hash conversion based on the quantization coefficients of each of the blocks so as to produce a hash value for each of the blocks; a digital watermark embedding unit which adjusts a parity of a quantization coefficient of interest equal to a parity of the has value of a block to which the quantization coefficient of interest belongs; and coding unit which generates code sequence data by coding the quantization coefficients including said quantization coefficient whose parity is adjusted.