# Frequency Analysis on DES, AES, 3DES using Cryptool2

I am trying to analyze symmetric block ciphers like DES, 3DES and AES, using Cryptool 2. I want to do a frequency analysis on each of these ciphers, in order to comment whether this is an effective way for cryptanalysis or not.

However, the ciphertext these ciphers produce comes in hex form:

My question is - when performing frequency analysis on such ciphers, do I input the hex ciphertext or do I need to transform it into text? How can I comment on that (based on letter frequency or bit occurrence)?

• Does this answer to your question? How can frequency analysis be applied to modern ciphers? Jul 2, 2020 at 14:28
• @kelalaka I read that before asking the question, but I didn't quite understand. I'm testing a random plaintext in English. From what I understand, I can perform frequency analysis on hex mode, and need to find general frequencies on english texts in hex mode in order to compare?
– C-Bk
Jul 2, 2020 at 14:35
• The frequency analysis on block cipher can work on block level. The data ( plaintext) in general is byte encoded. If one encrypts only one byte, then byte-level frequency works too. Of course, that requires non-randomized padding, too. In anyway, one need do compare 8 bytes for DES and 16 bytes for AES ciphertexts to observe a frequency due to the insecure mode ECB. If any other mode is used, like CBC and CTR mode then the modes have the standard Ind-CPA security and the attacker has no luck there Jul 2, 2020 at 14:38
• One doesn't exactly decrypt the ciphertext, one finds the value. Standard definition of decryption requires the key. Here, we cannot say how the plaintext are formed. They can be a date, name as in the example of the link. It is hidden in your question. If one knows the distribution of the plaintext then with ECB mode used, they can determine the plaintext with great probability. See the articles\ on the bottom of the linked answer. Jul 2, 2020 at 14:50
• @kelalaka: For you it is obvious that the frequencies for all symbols for these algorithms will be almost equal. But look at the goal in the OP: in order to comment whether this is an effective way for cryptanalysis or not. In my opinion, this is a reasonable task for a student - not to trust to what is said in a book, but to check if it really holds in particular case. Jul 2, 2020 at 20:36