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Article
Recovering DC coefficients in block-based DCT
IEEE Transactions on Image Processing
  • Takeyuki Uehara, University of Wollongong
  • Reihaneh Safavi-Naini, University of Wollongong
  • Philip Ogunbona, University of Wollongong
Document Type
Journal Article
Publication Date
1-1-2006
Abstract

It is a common approach for JPEG and MPEG encryption systems to provide higher protection for dc coefficients and less protection for ac coefficients. Some authors have employed a cryptographic encryption algorithm for the dc coefficients and left the ac coefficients to techniques based on random permutation lists which are known to be weak against known-plaintext and chosen-ciphertext attacks. In this paper we show that in block-based DCT, it is possible to recover dc coefficients from ac coefficients with reasonable image quality and show the insecurity of image encryption methods which rely on the encryption of dc values using a cryptoalgorithm. The method proposed in this paper combines dc recovery from ac coefficients and the fact that ac coefficients can be recovered using a chosen ciphertext attack. We demonstrate that a method proposed by Tang to encrypt and decrypt MPEG video can be completely broken.

RIS ID
16167
Citation Information
Takeyuki Uehara, Reihaneh Safavi-Naini and Philip Ogunbona. "Recovering DC coefficients in block-based DCT" IEEE Transactions on Image Processing Vol. 15 Iss. 11 (2006) p. 3592 - 3596
Available at: http://works.bepress.com/p_ogunbona/74/