# Questions tagged [rijndael]

Rijndael is a family of symmetric block-ciphers with block and keys sizes of 128, 160, 192, 224, or 256 bits.

88 questions
Filter by
Sorted by
Tagged with
2answers
432 views

### Is standardizing a modified AES a good idea?

"Recently" the Ukraine standardized a new block cipher Kalyna, which according to the abstract of"A New Encryption Standard of Ukraine: The Kalyna Block Cipher" by Oliynykov et al. (warning: the paper ...
1answer
37 views

### Rijndaelcipher mix column query

I quote a wikipedi para that says The operation consists in the modular multiplication of two four-term polynomials whose coefficients are elements of $\operatorname {GF} (2^{8})}$. ...
1answer
168 views

### AES reverse Rijndael key schedule with decryption round keys

I want to get the original encryption key (32 byte) of AES 256 (CBC) implementation. The implementation has the values of the inversed round keys values hard coded into the decryption function. I ...
0answers
75 views

### Is it possible to recover the key to a decrypted file? [duplicate]

Is it possible to recover the key to a decrypted file if you have the initialization vector and it uses RijndaelManaged in CBC mode? If so how? The file I want to recover the key from is a xml that ...
0answers
61 views

### Calculating the inverse for a Rijndael s-box [duplicate]

I want to calculate a Rijndael S-box but something went wrong. How can I calculate the inverse? In the following is my approach: given: $f(x)=x^8+x^4+x^3+x+1 \rightarrow$ binary: 100011011 0x12 = ...
1answer
62 views

### What is the difference between the 23 bi-affine and the 39 fully quadratic equations of the rijndael sbox?

In Cryptanalysis of Block Ciphers with Overdefined Systems of Equations Nicolas Courtois and Josef Pieprzyk define 23 so called bi-affine equations (in Appendix A of the paper) between the input x and ...
2answers
1k views

### Is there a contingency plan in the event of a catastrophic attack on AES?

NIST selected Rijndael in 2000 to be AES. In a paper from the Serpent authors, they mention that there was the possibility of choosing a second cipher as a backup in the case of any severe breaks: ...
1answer
2k views

### Can neural cryptanalysis be applied to AES?

In this Wikipedia article about Neural cryptography (section applications) it states: In 1995, Sebastien Dourlens applied neural networks to cryptanalyze DES by allowing the networks to learn how ...
1answer
131 views

### Implications of identical round keys in AES (Rijndael)

When reading up on the Rijndael key schedule, I learned that the master key itself is used as a round key directly before the key schedule generates additional round keys. When a 256-bit key is used, ...
1answer
857 views

### Confusion and Diffusion in the AES functions

I am pondering, how each of the four functions that a full AES round does consist of (Add Round Key, Substitute Bytes, Shift Rows and Mix Columns) add to the confusion and diffusion of the full AES. ...
1answer
102 views

### Any side effects of switching from Rijndael to AES in a .net application?

Our company would like to update our .Net apps so that they can run on Windows machines that require FIPS compliance. Currently we are using the System.Security.Cryptography.Rijndael class. I changed ...
0answers
86 views

1answer
145 views

### How does the Rijndael 192/256 bits block size mix column works?

I am quite comfortable about the 128 bits block size mix column operation, the maths behind it and how to implement it. However, what about the 192 and 256 bits block size? I can't find any paper ...
0answers
24 views

### Amount of key expansion rounds in AES [duplicate]

I am currently in the process of learning how AES actually works and that works great as of now but when it comes to the Rijndael's key schedule I have a question. From what I have read, I have to ...
1answer
262 views

### Why did they choose $x^4+1$ for the MixColumns step in Rijndael/AES?

In The Design of Rijndael page 39, It describe the design criteria for MixColumns step Dimensions. The transformation is a bricklayer transformation operatingon 4-byte columns. Linearity. The ...
1answer
377 views

### Prove the branch of number of Advanced Encryption Standard

In the Advanced Encryption Standard (AES) document: page 27 section 7.3.1, It defines branch number. It said " Let F be a linear transformation acting on byte vectors and let the byte weight ...
1answer
805 views

### Construction of S-box in AES

In my introductory cryptography class. There is a line describe the construction of S-box in AES "The S-box of AES is constructed by combining a function $h(x)=x^{254}$ defined on $GF(256)$ with an ...
1answer
180 views

### Can we have Rijndael s-boxes constructed using reducible polynomials?

Is it necessary for the Rijnael polynomial to be irreducible? Can we have s-boxes constructed using reducible polynomials? If not what is the mathematical property that is obstructing to do so?
1answer
1k views

### Is it necessary for the Rijndael polynomial to be primitive?

I am working on selecting a S-box for my Cipher (Similar to AES). I found out there are 30 irreducible polynomials and over 16 primitive polynomials of degree 8. Is it necessary to choose a primitive ...
1answer
1k views

### How to find the AES branch number?

By definition, branch number Definition: The branch number of a linear transformation $F$ is $$min_{a\neq0}(W(a) + W(F(a)))$$ Source here (7.3.1) For AES MixColumns $a \in GF(2^8)^4$ since ...
0answers
247 views

### Rijndael - is there some difference in resistance between counter in generator input and in IV?

I am thinking about Rijndael implementation in order to store tokens (cannot be hashed) - one token for one user. And finally I get stuck with key/IV generation problem :( The questions are: 1) Is ...
2answers
298 views

### Advantage of $\operatorname{GF}(2^8)$ over $\mathbb Z/2^8\mathbb Z$ in AES/Rijndael

The Galois Field is used in the mixColumns step of the Rijndael-Algorithm. Over $\operatorname{GF}(2^8)$ (irreducible polynomial: $x^8 + x^4 + x^3 + x + 1$), the ...
0answers
132 views

### Implement Twofish cipher with 16-bit blocksize?

I've seen implementation of Rijndael cipher with 16-bit blocksize. And I have also tried to implement 16-bit Rijndael cipher by myself with only a little sneak peeking at the example of the ...
0answers
649 views

### How can I find or reverse engineer the whitening in an AES algorithm?

I am working with this black box cryptography scheme. I know the plain text, cipher text, and everything else except how they whiten the data (or key?). Everything is 128 bit, 16 bytes. I have two ...
1answer
927 views

### Does changing the order of the steps within a round affect the security of AES?

I was trying to understand the internal structure of AES (Advanced Encryption Standard) Standard order of steps within a round: Substitute Bytes Shift Rows Mix Columns Add Round Key Substitute ...
1answer
269 views

### Increase in AES SBox

AES uses one single Sbox to substitute all 16 bytes in one Round. Will using 16 different Sboxes (with cryptographic properties similar to AES Sbox i.e Non-Linearity of 112, Differential probability ...
2answers
736 views

2answers
4k views

### AES encryption without salt and IV

I need to encrypt blocks of 16KiB with AES256. I have only one requirement to satisfy - If one day a hacker gets the data without the keys, he will not be able to decipher the data. According to the ...
4answers
22k views

### Found a way to crack AES-128, what now?

Let us assume the following scenario: I have just found a way to crack AES-128 in a reasonable time (1-2 days). How do I publish and prove this? I remember reading about lots of people who cracked ...
1answer
655 views

### RotWord in Rijndael's Algorithm

I am currently learning Rijndael's Algorithm through this site where there is a slide show animation step-by-step. I understand nearly all of the encryption process except part of Add Round Key....
1answer
426 views

### Probability of same input as output in AES 256

Note: I am assuming that, when entering in the key and plaintext, they are formatted in the same manner as the output of an AES-256 encrypted text. What is the probability, if any, that you could ...