Steganalysis of suspect media

1. A non-transitory computer-readable storage medium storing computer-executable instructions to process one or more instances of suspect media that include a plurality of data elements, the computer-executable instructions comprising:

dividing an instance of suspect media into non-overlapping consecutive blocks, wherein each of the non-overlapping consecutive blocks includes B×B data elements;

identifying a first quantized block of the data elements, wherein the first quantized block includes a first M×M subset of the data elements;

determining that the first M×M subset of the data elements is eligible to be embedded with steganographic data when the first M×M subset of data elements are identified within one B×B block of the non-overlapping consecutive blocks and not in two or more B×B blocks of the non-overlapping consecutive blocks;

identifying a second quantized block of the data elements, wherein the second quantized block includes a second M×M subset of the data elements;

determining that the second quantized block of the data elements is ineligible to be embedded with steganographic data when the second M×M subset of data elements are identified in two or more B×B blocks of the non-overlapping consecutive blocks and not within one B×B block of the non-overlapping consecutive blocks;

requantizing the first quantized block and the second quantized block of the data elements;

comparing statistics resulting from requantizing the first quantized block with further statistics resulting from requantizing the second quantized block; and

assessing whether the instance of suspect media is embedded with steganalytic features based on comparing the statistics to the further statistics.

2. The non-transitory computer-readable storage medium of claim 1 , further comprising receiving the one or more instances of suspect media as input for steganalytic processing, and wherein the data elements comprise pixels.

3. The non-transitory computer-readable storage medium of claim 2 , wherein receiving the one or more instances of suspect media comprises receiving one or more images, and wherein assessing whether the one or more instances of suspect media is embedded with steganalytic features comprises determining that at least one image is a stego-image, and extracting the steganalytic features from the image.

4. The non-transitory computer-readable storage medium of claim 3 , wherein receiving one or more images comprises receiving one or more JPEG images.

5. The non-transitory computer-readable storage medium of claim 1 , wherein comparing statistics comprises comparing a first quantity of zero-valued coefficients occurring in the statistics generated for the first quantized block to a second quantity of zero-valued coefficients occurring in the statistics generated for the second quantized block.

6. The non-transitory computer-readable storage medium of claim 5 , further comprising determining that the instance of the suspect media is stego-media when the first quantity of zero-valued coefficients occurring in the statistics for the first quantized block is determined to be greater than the second quantity of zero-valued coefficients occurring in the statistics for the second quantized block.

7. The non-transitory computer-readable storage medium of claim 5 , further comprising determining that the instance of the suspect media is non-stego-media when the first quantity of zero-valued coefficients occurring in the statistics for the first quantized block is determined to be approximately equal to the second quantity of zero-valued coefficients occurring in the statistics for the second quantized block.

8. The non-transitory computer-readable storage medium of claim 1 , wherein requantizing the first and second quantized blocks include performing a two-dimensional discrete cosine transformation (DCT) on the first and second quantized blocks to generate respective sets of DCT coefficients associated with the first and second quantized blocks, and rounding one or more of the DCT coefficients to have values of zero.

9. The non-transitory computer-readable storage medium of claim 1 , wherein the identifying the first and the second quantized blocks of data elements include defining two-dimensional blocks that includes two or more of the plurality of data elements.

10. The non-transitory computer-readable storage medium of claim 9 , wherein the first M×M subset of the data elements comprise a first 8×8 subset of the data elements; and wherein the second M×M subset of the data elements comprises a second 8×8 subset of the data elements.

11. The non-transitory computer-readable storage medium of claim 10 , wherein determining that the first M×M subset of the data elements is eligible to be embedded with stenographic data comprises identifying as eligible the first 8×8 subset of the data elements that fall entirely within one of the non-overlapping consecutive blocks.

12. The non-transitory computer-readable storage medium of claim 10 , wherein determining that the second M×M subset of the data elements is ineligible to be embedded with stenographic data comprises identifying as ineligible the second 8×8 subset of the data elements that span at least two of the non-overlapping consecutive blocks.

13. A non-transitory computer-readable storage medium storing computer-executable instructions to process one or more instances of stego-media that include a plurality of data elements, the computer-executable instructions comprising:

dividing a representation of the stego-media into a first two-dimensional block, wherein the first two-dimensional block comprises a first number of the plurality of data elements;

collecting a plurality of second two-dimensional blocks from within the first two-dimensional block, wherein each of the plurality of second two-dimensional blocks comprises a second number of data elements, wherein the second number of data elements is less than or equal to the first number of data elements;

performing a two-dimensional discrete cosine transformation (DCT) on the plurality of second two-dimensional blocks;

quantizing DCT coefficients that result from the two-dimensional DCT;

computing a frequency at which rounded values of the DCT coefficients substantially equal zero, wherein the frequency comprises a ratio of the rounded values of the DCT coefficients that substantially equal zero relative to a total number of the rounded values of the DCT coefficients including rounded values of the DCT coefficients that do not substantially equal zero; and

extracting stego features from the stego-media based at least in part on the computed frequency at which the DCT coefficients have rounded values of substantially zero.

14. The non-transitory computer-readable storage medium of claim 13 , further comprising collecting the plurality of second two-dimensional blocks such that blocks having 8×8 data elements are collected.

15. The non-transitory computer-readable storage medium of claim 13 , further comprising cropping a plurality of rows and columns from an image to generate a further image as a subset of the image, wherein the image is associated with the instance of the stego media.

16. The non-transitory computer-readable storage medium of claim 15 , further comprising extracting steganographic features from the further image.

17. The non-transitory computer-readable storage medium of claim 13 , wherein the instance of the stego media is associated with a JPEG image.

18. The non-transitory computer-readable storage medium of claim 13 , wherein a processor is further configured in cooperation with the computer-readable storage medium to transfer the instance of the stego media from the computer-readable storage medium to a memory.

19. An apparatus configured to process one or more instances of suspect media that includes a plurality of data elements, the apparatus comprising:

a processor; and

a computer-readable storage medium containing computer-executable instructions which are executed by the processor and cause the processor to:

divide the suspect media into non-overlapping consecutive blocks, wherein each of the non-overlapping consecutive blocks includes B×B data elements;

identify a first quantized block of the data elements, wherein the first quantized block includes a first M×M subset of the data elements;

determine that the first M×M subset of the data elements is eligible to be embedded with steganographic data when the first M×M subset of data elements are identified within one B×B block of the non-overlapping consecutive blocks and not in two or more B×B blocks of the non-overlapping consecutive blocks;

identify a second quantized block of the data elements, wherein the second quantized block includes a second M×M subset of the data elements;

determine that the second quantized block of the data elements is ineligible to be embedded with steganographic data when the second M×M subset of data elements are identified in two or more of the non-overlapping consecutive blocks and not within one B×B block of the non-overlapping consecutive blocks;

requantize the first quantized block and the second quantized block of the data elements;

compare statistics resulting from requantizing the first quantized block with further statistics resulting from requantizing the second quantized block; and

assess whether the suspect media is embedded with steganographic features based on comparing the statistics with the further statistics.

20. The apparatus of claim 19 , wherein the data elements comprise pixels of an image.

21. The apparatus of claim 20 , wherein the image comprises a JPEG image.

22. An apparatus configured to process one or more instances of stego-media that includes a plurality of data elements, the apparatus comprising:

a processor; and

a computer-readable storage medium containing computer-executable instructions which are executed by the processor and cause the processor to:

divide a representation of the stego-media into a first two-dimensional block, wherein the first two-dimensional block comprises a first number of the plurality of data elements;

collect a plurality of second two-dimensional blocks from within the first two-dimensional block, wherein each of the plurality of second two-dimensional blocks comprises a second number of data elements, wherein the second number of data elements is less than or equal to the first number of data elements;

perform a two-dimensional discrete cosine transformation (DCT) on the plurality of second two-dimensional blocks;

quantize DCT coefficients that result from the two-dimensional DCT;

compute a frequency at which rounded values of the DCT coefficients substantially equal zero, wherein the frequency comprises a ratio of the rounded values of the DCT coefficients that substantially equal zero relative to a total number of the rounded values of the DCT coefficients including rounded values of the DCT coefficients that do not substantially equal zero; and

extract stego features from the stego-media based at least in part on the computed frequency at which the DCT coefficients have rounded values of substantially zero.

23. The apparatus of claim 22 , wherein the data elements comprise pixels of an image.

24. The apparatus of claim 23 , wherein the image comprises a JPEG image.