Notice: RCIS was reformed into RISEC on April 1, 2012.
It has been further merged into new Information Technology Research Institute on April 1, 2015.

Research Topics
AIST > RCIS > Research Topics > Secure fingerprinting codes for digital watermarking

Secure fingerprinting codes for digital watermarking


For network distribution services of copyrighted digital data (such as pay web distribution of musics, or digital libraries), the possibility of illegal redistribution due to some licensed user, who obtained the data in a legal way from the server, should be considered. Such actions cannot be prevented by use of encrypted communication only. To prevent the illegal copying itself is not realistic, because digital data can be in general copied easily, without decreasing its quality. An alternative solution investigated recently is ``digital watermarking'', which is a technology to embed some auxiliary information into digital data. In this case, the server embeds certain identification information of each user into the data before distributing (in this case, this technique is called ``fingerprinting''). Then, when the server finds the illegal copy, embedded information enables him to detect the guilty user.

However, if the server embeds user IDs (or its numerical expressions) simply, two or more colluded users can recognize easily the position of embedded information by comparing their data legally obtained. As a consequence, embedded information may be erased by the colluded users. Furthermore, it may be also possible even to forge the data which contain ``identification information of other innocent user''.

For the purpose of coping with such illegal actions by colluded users, we have been investigating construction of suitable embedded information, namely conversion method (encoding) from user IDs to embedded information.


  • Manabu Hagiwara
  • Takashi Kitagawa
  • Koji Nuida
  • Hajime Watanabe


Some of this research has been sponsored by the Ministry of Economy, Trade and Industry, Japan (METI) under contract, New-generation Information Security R&D Program (FY 2005 - FY 2007).

Some of this research has been sponsored by Ministry of Education, Culture, Sports, Science and Technology (MEXT) Grant-in-Aid for Young Scientists (B) (No. 16700021) (FY 2004 - FY 2006).

Selected Results

  1. H.Watanabe and T.Kitagawa, ``An ID Coding Scheme for Fingerprinting, Randomized c-secure CRT Code,'' Proceedings of ICICS2002 (Fourth International Conference on Information and Communications Security), LNCS 2513, pp.173-183, Singapore, Dec. 2002.
  2. H.Watanabe and T.Kitagawa, ``A Random-Error-Resilient Collusion-Secure Fingerprinting Code, Randomized c-Secure CRT Code,'' IEICE Transactions on Fundamentals, vol.E86-A, no.10, pp.2589-2595, Oct. 2003.
  3. M.Hagiwara, G.Hanaoka, and H.Imai, ``A Short Random Fingerprinting Code Against a Small Number of Pirates,'' Proceedings of AAECC2006 (16th AAECC Symposium Applied Algebra, Algebraic Algorithms, and Error Correcting Codes), LNCS 3857, pp.193--202, USA, Feb. 2006.
  4. K.Nuida, M.Hagiwara, H.Watanabe, and H.Imai, ``Optimization of Tardos's fingerprinting codes in a viewpoint of memory amount,'' Proceedings of IH 2007 (9th Information Hiding), LNCS 4567, pp.279--293, France, June 2007.
  5. K.Nuida, S.Fujitsu, M.Hagiwara, T.Kitagawa, H.Watanabe, K.Ogawa, and H.Imai, ``An improvement of Tardos's collusion-secure fingerprinting codes with very short lengths,'' Proceedings of AAECC-17 (17th Symposium on Applied Algebra, Algebraic Algorithms and Error-Correcting Codes), LNCS 4851, pp.80--89, India, Dec. 2007.