The difference between a .CR2 or .NEF file and a DNG is that you can work the RAW file and then save to DNG and it appears unedited, you have clearly already edited the Canon file. What tiny bit of credibility you had due to your obviously limited but deep knowledge of one specific of a sensor has just been blown out of the water.
Mikael, you are an irrelevance.
Now I'm interested. Please show me a set of files - one .cr2 and one .dng made from that cr2 file - where the image data inside the DNG has been significantly altered...?
Of course it can be done. I could change the content of just about any raw file from any camera maker. Canon and some others have a control sum data tag that is supposed to protect against that kind of tampering, but that checksum encoding has been cracked since several years. So it's definitely not impossible, it just takes some work.
What I question is the general availability of those tools, and that you think that just about anyone can do it. AND the fact that you erroneously think that any normal program can change the image content of a raw file before saving it as a DNG. Yes, some EXIF tags may be repositioned, and some extra data may be saved - but the original image data is copied in a bit-perfect way. Bit-perfect as in "no single bit of the resulting image surface has changed between the original raw and the dng".(actually that isn't 100% true, only 99.999% - Since Nikon and also Sony can use a kind of gamma / area coherency compression when saving a raw file, round-off faults in the conversion can appear since the DNG is LS-JPEG compressed, without gamma. That is, errors on the scale of +/-1 bit in a 14-bit file, or errors more than 13Ev down)
But still, show me the two files where the DNG has been seriously and provably tampered with. YOUR files, not someone elses.