Using CrypTool I encrypted a plaintext with "DES CBC" and I genereated the histogram of plaintext and ciphertext. The histogram shows the relative frequency of each of the characters in the document.
When I did the same with "Caesar" cipher based on online tutorials, it was possible to find the correlation between some characters comparing their frequency that I could see in their histograms.
But that it is not possible for DES. I try to find out why this is not possible. What properties of the DES are responsible for this?