Can a Feistel cipher be accurately evaluated by a third party?

  • Thread starter Chris Miller
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In summary, the conversation discusses a block cipher based on a Feistel network that is smaller, faster, and simpler than AES. The cipher uses a table of 32-bit values as an s-box, which can be populated with random sequences or scheduled as part of the key. The speaker is looking for someone to examine the cipher and potentially decode a message using it, but acknowledges that it may be difficult without access to certain attack methods.
  • #1
Chris Miller
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I've developed a block cipher based on a Feistel network that is, round for round, smaller (4 steps) and faster (by 15 to 40 percent) than AES (aka Rijndael), and way simpler. I'd like to say stronger, too, but cannot support this assertion myself. Proprietary configurations are easy to create. Because it's a Feistel network (vs. a Substitution Permutation Network like AES), the s-box (an expansion p-box actually) , which is a table of 256 (or 1024 or 2048 in some flavors) 32-bit values, can be populated with virtually any normal random sequence, or even scheduled as part of the key. As with AES, it exhibits BIC and SAC compliance in two rounds.

My question is, is there any way of having it examined, if only cursorily, by someone better educated and experienced?
 
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  • #2
Post the source code on a website, social network, or programming site and a challenge of decrypting a message that you supply (maybe a random paragraph from your favorite novel). 'Reward' can be anything from a 'Thank You', to acknowledgment in the distribution version, a custom T-shirt, or perhaps $50 to the first correct decode.

Cheers,
Tom
 
  • #3
Thanks Tom, but I am 100 percent sure no one is going to decrypt the cipertext of even a mediocre 128-bit multi-round Feistel cipher without at least the ability to mount a chosen plaintext or chosen ciphertext attack (i.e., oracle access). For me to invite someone to try strikes me as a little naive. Like just providing 1 block (16 bytes) of ciphertext, a simple XOR of the plaintext message with the key (i.e., a one-time pad) would be enough to prevent decryption.
 

FAQ: Can a Feistel cipher be accurately evaluated by a third party?

1. How do you determine the authenticity of a cipher?

To determine the authenticity of a cipher, there are a few key steps to follow. First, examine the source of the cipher and its intended use. Is it from a trusted source, and is it being used for a legitimate purpose? Next, analyze the structure and patterns of the cipher. Is it using a well-known and secure encryption method, or does it seem suspiciously complex or convoluted? Finally, test the cipher by applying it to a known message and comparing the resulting ciphertext to the expected output. If the cipher holds up to all of these tests, it is likely authentic.

2. What are the common techniques used to break ciphers?

There are several common techniques that can be used to break ciphers, including frequency analysis, brute force attacks, and known-plaintext attacks. Frequency analysis involves analyzing the frequency of letters or patterns in the ciphertext to identify potential substitutions. Brute force attacks involve systematically trying every possible key or combination of keys until the correct one is found. Known-plaintext attacks take advantage of known information about the plaintext and corresponding ciphertext to decipher the message. Ultimately, the most effective technique will depend on the type and strength of the cipher being used.

3. How does the key affect the security of a cipher?

The key is a crucial component of any cipher, as it determines the specific encryption and decryption process used. The length and complexity of the key can greatly impact the security of a cipher. A longer and more complex key is generally more secure as it makes it more difficult for an attacker to guess or brute force the key. Additionally, the strength of the cipher's algorithm also plays a significant role in the overall security, as a weak algorithm combined with a strong key may still result in a vulnerable cipher.

4. Can a cipher be completely unbreakable?

No cipher can be considered completely unbreakable, as any encrypted message can potentially be decrypted with enough time and resources. However, some ciphers are significantly stronger and more difficult to break than others, making them practically unbreakable given current technology and techniques. Additionally, consistently updating and improving ciphers can help maintain their security against evolving attacks.

5. How can one verify the strength of a cipher?

There are several ways to verify the strength of a cipher. One approach is to conduct cryptanalysis, which involves testing the cipher against known attacks and measuring its resistance. Another way is to seek out expert opinions and reviews from trusted sources in the field of cryptography. Additionally, regularly updating and improving a cipher can help maintain its strength against potential attacks and vulnerabilities.

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