cryptanalysis

Is it possible to reverse engineer AES256?

Imagine I have this: $cdata = AES_256($data, $pass); AES_256 algorithm is: http://en.wikipedia.org/wiki/Advanced_Encryption_Standard If I know the content of $cdata and the content of $data and also have the AES256() code, can I reverse engineer and find $pass? ...

How to predict the next GUID from a given GUID?

Hi, i have sent 10000 mails to our customers and each mail had a link of the format http://example.com/LogIn?key={guid} unfortunately the guid i sent were random guids (test data generated by Guid.NewGuid()) so the customers have all received invalid links... based on the 404s i receive from the webserver i have a few guids that i sent...

What is the difference between a multi-collision and a first or second pre-image attack on a hash function?

What is the difference between a multi-collision in a hash function and a first or second preimage. First preimage attacks: given a hash h, find a message m such that hash(m) = h. Second preimage attacks: given a fixed message m1, find a different message m2 such that hash(m2) = hash(m1). Multi-collision attacks: generate a series o...

Transposition or Substitution Ciphertext? (monoalphabetic or polyalphabetic?)

Hi, We have a ciphertext with IC=0.0685. We want to find out the class descriptor (mono-alphabetical/poly-alphabetical/transposition). I have applied the 2 probabilistic tests to try and guess what class it belongs to. These tests are: Ratio of vowels to total (<25%) then more likely a substitution %ETAOS in text (<35%) then more likel...

How do brute force decryption attacks know when they've found the right solution?

How do brute-force attacks on encrypted data know when they've found the right key to decrypt the data? Is there a way to know that data's been decrypted, other than having a human looking at it? What if it's not human-friendly data? ...

Isn't it difficult to recognize a successful decryption?

When I hear about methods for breaking encryption algorithms, I notice there is often focused on how to decrypt very rapidly and how to reduce the search space. However, I always wonder how you can recognize a successful decryption, and why this doesn't form a bottleneck. Or is it often assumed that a encrypted/decrypted pair is known? ...

spatial ciphers/cryptanalysis techniques based on neighborhood spaces in a grid?

Are there spatial ciphers/cryptanalysis techniques based on neighborhood spaces in a grid? More specially are there 5 orientation spaces with the values being north, south, east, west, neutral? Thanks for the help guys. I know this sounds more like rigorous math, but just need a simple explanation or some direction, as in resources or ...