scholarly journals JPEG image steganography payload location based on optimal estimation of cover co-frequency sub-image

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Jie Wang ◽  
Chunfang Yang ◽  
Ma Zhu ◽  
Xiaofeng Song ◽  
Yuan Liu ◽  
...  
Keyword(s):  
Markov Model ◽  
Optimal Estimation ◽  
Image Steganography ◽  
Absolute Difference ◽  
Low Frequencies ◽  
Jpeg Image ◽  
Location Method ◽  
Average Residual ◽  
Dct Coefficients ◽  
Maximum A Posterior

AbstractThe excellent cover estimation is very important to the payload location of JPEG image steganography. But it is still hard to exactly estimate the quantized DCT coefficients in cover JPEG image. Therefore, this paper proposes a JPEG image steganography payload location method based on optimal estimation of cover co-frequency sub-image, which estimates the cover JPEG image based on the Markov model of co-frequency sub-image. The proposed method combines the coefficients of the same position in each 8 × 8 block in the JPEG image to obtain 64 co-frequency sub-images and then uses the maximum a posterior (MAP) probability algorithm to find the optimal estimations of cover co-frequency sub-images by the Markov model. Then, the residual of each DCT coefficient is obtained by computing the absolute difference between it and the estimated cover version of it, and the average residual over coefficients in the same position of multiple stego images embedded along the same path is used to estimate the stego position. The experimental results show that the proposed payload location method can significantly improve the locating accuracy of the stego positions in low frequencies.

scholarly journals Payload location for JPEG image steganography based on co-frequency sub-image filtering

2020 ◽  
Vol 16 (1) ◽  
pp. 155014771989956 ◽  
Author(s):  
Jie Wang ◽  
Chunfang Yang ◽  
Ping Wang ◽  
Xiaofeng Song ◽  
Jicang Lu
Keyword(s):  
Discrete Cosine Transform ◽  
Estimation Method ◽  
Image Filtering ◽  
Image Steganography ◽  
Experimental Results ◽  
Jpeg Image ◽  
Image Estimation ◽  
Location Method ◽  
Transform Coefficients ◽  
The Mean

In digital steganography, due to difficulties estimating the JPEG cover image, it is still very hard to accurately locate the hidden message embedded in a JPEG image. Therefore, this study proposes a payload location method for a category of pseudo-random scrambled JPEG image steganography. In order to estimate the quantized discrete cosine transform coefficients in the cover JPEG image, a cover JPEG image estimation method is proposed based on co-frequency sub-image filtering. The proposed payload location method defines a general residual, uses the estimated cover JPEG image to compute the residuals, and then employs the mean residuals of multiple stego images embedded along the same path to distinguish the stego positions. The proposed cover JPEG image estimation method constructs 64 co-frequency sub-images, and then filters the sub-image to estimate the cover JPEG image. Finally, using these methods, payload location algorithms are designed for two common JPEG image steganography algorithms: JSteg and F5. Experimental results show that the proposed location algorithms can effectively locate the stego positions in both JSteg and F5 steganography when the investigator possesses multiple stego images embedded along the same path. In addition, the location results can also be used to recover the steganography key to extract the embedded secret messages.

Generation of Low-Frequency Spiciness Variability in the Thermocline*

2011 ◽  
Vol 41 (2) ◽  
pp. 365-377 ◽  
Author(s):  
Thomas Kilpatrick ◽  
Niklas Schneider ◽  
Emanuele Di Lorenzo
Keyword(s):  
Markov Model ◽  
Large Scale ◽  
Spatial Scales ◽  
Low Frequency ◽  
Passive Tracer ◽  
Wind Stress Curl ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Geostrophic Advection

Abstract The generation of variance by anomalous advection of a passive tracer in the thermocline is investigated using the example of density-compensated temperature and salinity anomalies, or spiciness. A coupled Markov model is developed in which wind stress curl forces the large-scale baroclinic ocean pressure that in turn controls the anomalous geostrophic advection of spiciness. The “double integration” of white noise atmospheric forcing by this Markov model results in a frequency (ω) spectrum of large-scale spiciness proportional to ω−4, so that spiciness variability is concentrated at low frequencies. An eddy-permitting regional model hindcast of the northeast Pacific (1950–2007) confirms that time series of large-scale spiciness variability are exceptionally smooth, with frequency spectra ∝ ω−4 for frequencies greater than 0.2 cpy. At shorter spatial scales (wavelengths less than ∼500 km), the spiciness frequency spectrum is whitened by mesoscale eddies, but this eddy-forced variability can be filtered out by spatially averaging. Large-scale and long-term measurements are needed to observe the variance of spiciness or any other passive tracer subject to anomalous advection in the thermocline.

Empirical and theoretical analysis of the extremely low frequency arterial blood pressure power spectrum in unanesthetized rat

2006 ◽  
Vol 291 (6) ◽  
pp. H2816-H2824 ◽  
Author(s):  
David R. Brown ◽  
Lisa A. Cassis ◽  
Dennis L. Silcox ◽  
Laura V. Brown ◽  
David C. Randall
Keyword(s):  
Blood Pressure ◽  
Time Series ◽  
Power Spectrum ◽  
Arterial Blood Pressure ◽  
Low Frequency ◽  
Absolute Difference ◽  
Frequency Range ◽  
Low Frequencies ◽  
Extremely Low Frequency ◽  
Arterial Blood

The slope of the log of power versus the log of frequency in the arterial blood pressure (BP) power spectrum is classically considered constant over the low-frequency range (i.e., “fractal” behavior), and is quantified by β in the relationship “1/ fβ.” In practice, the fractal range cannot extend to indefinitely low frequencies, but factor(s) that terminate this behavior, and determine β, are unclear. We present 1) data in rats ( n = 8) that reveal an extremely low frequency spectral region (0.083–1 cycle/h), where β approaches 0 (i.e., the “shoulder”); and 2) a model that 1) predicts realistic values of β within that range of the spectrum that conforms to fractal dynamics (∼1–60 cycles/h), 2) offers an explanation for the shoulder, and 3) predicts that the “successive difference” in mean BP (mBP) is an important parameter of circulatory function. We recorded BP for up to 16 days. The absolute difference between successive mBP samples at 0.1 Hz (the successive difference, or Δ) was 1.87 ± 0.21 mmHg (means ± SD). We calculated β for three frequency ranges: 1) 0.083–1; 2) 1–6; and 3) 6–60 cycles/h. The β for all three regions differed ( P < 0.01). For the two higher frequency ranges, β indicated a fractal relationship (β6–60/h = 1.27 ± 0.01; β1–6/h = 1.80 ± 0.16). Conversely, the slope of the lowest frequency region (i.e., the shoulder) was nearly flat (β0.083–1 /h = 0.32 ± 0.28). We simulated the BP time series as a random walk about 100 mmHg with ranges above and below of 10, 30, and 50 mmHg and with Δ from 0.5 to 2.5. The spectrum for the conditions mimicking actual BP time series (i.e., range, 85–115 mmHg; Δ, 2.00) resembled the observed spectra, with β in the lowest frequency range = 0.207 and fractal-like behavior in the two higher frequency ranges (β = 1.707 and 2.057). We suggest that the combined actions of mechanisms limiting the excursion of arterial BP produce the shoulder in the spectrum and that Δ contributes to determining β.

scholarly journals Analysis of JPEG Image Steganography using Least Significant Bit Method

2019 ◽  
Vol 14 (14) ◽  
pp. 4849-4852
Author(s):  
Jordy Ardian Bagaskara ◽  
Tito Waluyo Purboyo ◽  
Ratna Astuti Nugrahaeni
Keyword(s):  
Image Steganography ◽  
Least Significant Bit ◽  
Jpeg Image

scholarly journals Ground-based measurements of middle-atmospheric carbon monoxide above Ny-Ålesund (78.9° N, 11.9° E)

2019 ◽  
Author(s):  
Niall J. Ryan ◽  
Mathias Palm ◽  
Christoph G. Hoffmann ◽  
Jens Goliasch ◽  
Justus Notholt
Keyword(s):  
Carbon Monoxide ◽  
Middle Atmosphere ◽  
A Priori ◽  
Optimal Estimation ◽  
Low Noise ◽  
Absolute Difference ◽  
Atmospheric Measurements ◽  
Mixing Ratios ◽  
Atmospheric Carbon ◽  
Atmospheric Carbon Monoxide

Abstract. We present a new ground-based system for measurements of middle-atmospheric carbon monoxide (CO) at Ny Ålesund, Svalbard, and the altitude profiles of CO volume mixing ratios (VMR) measured during the 2017/2018 winter. The Carbon Monoxide Radiometer for Atmospheric Measurements (CORAM) records spectra from CO emissions in the middle-atmosphere with the aid of a low-noise amplifier designed for the 230 GHz spectral region. Altitude profiles of CO VMRs are retrieved from the measured spectra using an optimal estimation inversion technique. The profiles in the current dataset have an average altitude range of 47–87 km and an estimated precision peaking at ~ 12 % of the a priori used in the inversion. The CORAM profiles are compared to collocated CO measurements from the Microwave Limb Sounder (MLS) aboard the Aura satellite and show a difference of 7.4–16.1 %, with a maximum absolute difference of 2.5 ppmv at 86 km altitude. CO profiles are currently available at 1 hr resolution between November 2017 and January 2018.

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