Video surveillance of both public and private spaces is expanding at
an ever-increasing rate. Consequently, individuals are increasingly
concerned about the invasiveness of such ubiquitous surveillance and
fear that their privacy is at risk. The demands of law enforcement
agencies to prevent and prosecute criminal activity, and the need
for private organizations to protect against unauthorized activities
on their premises are often seen to be in conflict with the privacy
requirements of individuals.
The Secure Shape and Texture Set Partitioning in Hierarchical Trees
(SecST-SPIHT) secure visual object coder was developed to address this. The SecST-SPIHT scheme codes the shape and texture of
arbitrarily-shaped visual objects in the same fashion as ST-SPIHT
[1], employing a shape-adaptive discrete wavelet
transform (SA-DWT) variant and a modified SPIHT
algorithm offering progressive/embedded bit-rate
output. The proposed scheme incorporates a novel selective
encryption algorithm, utilizing a stream cipher to encrypt a small
portion of the output bit-stream. The activation of the cipher is
controlled by intelligent bit-classification instructions received
from the coder. The scheme efficiently and effectively secures the
entire shape and texture of the object and ensures that the object
cannot be reconstructed without provision of the correct decryption
key; no object details are revealed without providing the exact,
correct decryption key. At typical output bit-rates and choice of
security parameter, the encryption operation is performed on less
than 5% of the output code bits; the remaining unencrypted code
bits cannot be decoded due to their dependence on the correct
interpretation of the encrypted portion of the code. The
progressive/embedded nature of the coder allows the output bit-rate
to be varied without affecting the total number of encrypted bits or
reducing security.

Original surveillance frame
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 Object texture encrypted using SecST-SPIHT |
 Object texture and shape encrypted using SecST-SPIHT |
The SecST-SPIHT secure coder can be employed in surveillance systems
where the capture of certain visual objects may be considered
privacy invasive (e.g., face and body images). The decryption key
required to decrypt and decode the visual object shape and texture
may be managed such that only the appropriate authorities are able
to access the object data. Furthermore, the key may be tied to the
subject's identity (e.g., through RFID based tokens), thus giving
control of the private content to the subject. The selective encryption procedure makes the scheme suitable for
real-time applications where significant processing resources are
requisitely consumed for coding of the video stream and traditional
"whole content" encryption may be computationally infeasible.
Read the full Technical Report (2008.01) »
[1] K. Martin, R. Lukac, K.N.
Plataniotis, "SPIHT-Based Coding of the Shape and Texture of Arbitrarily Shaped Visual Objects," IEEE Transactions on Circuits and Systems for Video Technology, vol. 16, no. 10, pp. 1196-1208, Oct. 2006..