G1 Undergrad at CU Just something hopefully easy to get started. Crack the cipher. (Note: the spaces are just grouping, the underscores are the real spaces.)
WOTHL EMOEU LE__B C_TC!
G2 Master's Program To get a Master's Degree or Ph.D at CU you must analyze this encryption program I just made.
You choose a key, which can be any number really. The ith letter is encrypted like this: [eqn]cipher_i = [ message_i + (key*(i+1)\mod 95 ) ] \mod 95 [/eqn] Which produces a random (based on the key) value between 0 and 94, add 32 to get an ASCII character.
You can use the program by typing these commands:
encrypt(42046,"I'm pregnant")
Output: "8WBkFqL,W={
G2: Tell me which values would not be effective as keys.
G3 PhD Program (I do not know the answers to these questions, nobody does, that is why it is PhD level )
Either find a way to crack this cipher 80pnt{n?AZY?ygA*fb0}mG&hK@y[Y
OR you can also find some kind of attack or vulnerability with the system. Let me know if chosen plaintext or any other information can help you crack the cipher.
How else is it vulnerable? Given a known plaintext, I'm pretty sure it would be infeasible to compute the key. But length extension attacks are still possible with how this is set up. Maybe the program should apply a transposition function also?
Here is a super secret message if you feel like cracking it:
>Not IND-CPA secure The pitfalls here are self-explanatory.
>Key recovery attack vulnerability for known plaintexts If I can choose a single block of the message to be encrypted, and if I choose that block to be zero, I can recover the key immediately using simple field operations upon receiving the ciphertext.
Please don't try to use this in an application environment.
>t. person with real graduate degree in cryptography
Jose Wright
Ok cool thanks for posting.
>I can recover the key immediately using simple field operations Can you explain this more, and how you would specifically do it to this program ?
Can you walk me through any kind of other method to crack these ciphers?
>Please don't try to use this in an application environment. Cryptography Club is just for fun, we post challenges for each other to crack.
Brayden Kelly
this only expands the key to 95*95
through bruteforce the message is May 23rd, 2017
the name is still merkle
Justin Reyes
Amazing!
>this only expands the key to 95*95
I really want to know how you got that?? Thank you.
Eli Gutierrez
the addition of sKey is basically a caesar cipher so it shifts each letter by some amount
so you have the original key with length 95 and the shift which is 95 because of the mod 95
you can then bruteforce by decrypting using all 95 keys (0-95) then shift the decrypted message by 0-95 until you find something that looks like message or use frequency analysis
Jack Moore
Starting at a PhD program in math this fall and cryptography is my main research interest. Can you recommend any readings, textbooks, or research papers? Any general advice?
Logan Lopez
Crazy shit man, crazy.
Christopher Cox
My biggest suggestion is to not skimp on your knowledge of theoretical computer science. Most of the math-crypto specialists I know develop almost entirely out of an appreciation of the aesthetics behind constructing a primitive in a specific manner, often at the cost of their understanding of how to develop primitives which serve real-world purposes and offer real-world security.
I would also suggest picking up some of the more practical aspects (and vulnerabilities) of cryptography, especially those related to implementation. It won't be your primary interest as a cryptographer, but an entire sub-section of the field is devoted to developing methods to address such vulnerabilities.
Jaxson Garcia
how do i get started with cryptography? any books?
good personal projects to start with?
Carson Ortiz
bump
David Scott
Step 1: Understand what cryptography is enough to be able to summarize the most common goals. Step 2: Pick any of the fundamental goals (e.g. symmetric-key encryption, collision-resistant hashing, ...). Step 3: Study that goal in detail until you understand the terminology and the precise formal statement of said goal. Step 4: Choose an industrial-strength construction for said goal and understand it. Step 5: Go to step 2
Henry Sanders
>good personal projects to start with?
Go to r/codes and r/ARG, try to solve the codes there. Create your own codes for people to solve. Also try to make your own encryption or hash algorithm.
