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Hermetic Stego compresses the data file before hiding it in the BMP stego image files. BMP files consist mainly of color bytes. Thus if we assume that the data file can be compressed to 50% of its size before hiding, and that on average one byte of the data file will be stored in ten bytes of the stego image files, we have a rough general rule that to store a data file of n KB we need stego images totalling 5*n KB. So, for example, to store a data file 1 MB in size (= 1024 KB) in 10 stego images then the average size of those images must be 5*1024/50 = 510 KB. It is thus impractical to hide a data file of 1 GB (= 1024 KB) or more because this would require, more than 1000 images of average size 5 MB.
There are two restrictions pertaining to the input image files:
- The input image folder cannot contain more than 400 BMP image files.
- The total size of the input image files cannot exceed 2000 MB.
Thus if, e.g., 200 input image files are used then their average size cannot exceed 10 MB.
Under the assumption in the first paragraph this places a restriction on the maximum size of the data file, namely, 200 MB. Thus the software does not accept a data file with a size of more than 250 MB.
An attempt to hide a data file more than 100 MB in size will likely result in a message that there are not enough image files to hide the data.
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