f.J .J £唧 f Chongqing University-Eng
.
Ed. June 20
Using the W avelet as the Private Key for Encrypting the W atermark。
YANG Xiaofan,W U Zhongfu,LIAO Xiaofeng
College of Computer Science,Chongqing University,Chongqing 4OOO44,P
. R.China
Received 22 February 2002:revised 29 April 2002
Abstract:Waterm arking is an effective approach to the copyright protection of digital media such as audio,
image,and video.By inspiration from cryptography an d considering the .m mens of the set of all possible
wavelets,it is presented that in wavelet domain waterm arking,the associated wavelet can be considered as
the private key for encrypting the waterm ark so as to enhance the security of the embedded mark.This idea
is partly suppo rted by the fact that fr0m computational com plexity viewpoint. it is very time-consuming to
search over the immense set of all candidate wavelets for the right one if no a priori knowledge is known
about it.To verify our propo sal,the stan dard im age“Lena” is first watermarked in a specific wavelet doma—
in,the waterm ark recovery experiments are then co nducted in the wavelet domain for a set of wavelets w ith
the one used for ma rk em bedded in it.separately. It follows f the experim ental results that the ma rk can
be rec overed only in the right wavelet domain,which justifies the suggestion.
Keywords: Digital waterm ark; Waterm arking; Cry ptography; Private key cry ptographic system ; W avelet;
DaLJbechies wavelet
1 I ntroduction
Digital media (such as audio, image,video ,
etc.)have revolutionized the way data are stored,
man ipulated an d transmi ̄ed,giving rise to a wide
range of new applic ̄ions(including digital televi—
sion,digital image database,elec tronic publishing,
etc.).One of the main features of digital technolo—
gY is the ease with wh ich data can be accessed
an d duplicated.This feature, however, makes it a
trivial work to reproduce and redistribute an unlimit—
ed am ount of unauthorized perfec t copies of the
original data,i.e.data piracy.Due to this,co PY—
right protec tion of digital media has become a very
impo rtant issue l1—5].
Techniques based on cryptography can be used
for countering digital piracy in this way:Encrypted
products are accessible, wh ereas decry ption is
po ssible only by som eo ne wh o po ssess es a proper
key[6].Cryptographic systems are not enough for
copyright protection since once the encry pted data
is decrypted there is no more means to track its re-
production or dissemination.Digital waterm arking is
intended to co m plem ent cry ptographic tec hniques
[1-5].A digital watermark is a signal that is em —
bedded in a digital wo rk wh ich allows one to estab—
lish ownership,to identify a buyer,an d/or provide
som e additional inform ation.For most practical ap—
plications,the waterm ark should be perceptually in一
· Foundation item :Funded by the visit scholar Foundation of the Electrooptical Technique & System key Lab of Chinese M in—
istry of Education in Cho ngqing.
Authorbrief:YANG Xiaofan(杨 小 帆 ):Male;Bom 1964;PhD;P .;Ma in research scopes:image and video co ̄ res—
sion ,waterm arking,neural network ,network and parallel com putation.