Questions tagged [rijndael]

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

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Is there a common method for a virtual two way dictionary of statistically independent random values with a domain size of about 192bit? (like ECB BC)

Is there any commonly used dictionary/codebook like function $D$ which assigns for every value $r_i \in V=[0,s-1]$ with $s\approx 2^{200}$ a value $r_j$ also $\in V$ $$D(r_i) = r_j$$ and is self-...
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Bringing a key to 256 bit by a hash algorithm

For example, if I use Rijndael for encryption, I have to specify a key of a certain length. For user convenience, I want the user to be able to use a key of any length. Then, to get the key to the ...
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AES MixColumn Polynomial Transformation [duplicate]

I just read about the AES MixColumn step, which can be calculated as: $$b(x)=c(x)a(x) \pmod{X^4 +1}$$ $a(x)$ is the column to encode and $c(x)=3x^3+x^2+x+2$ My question is: how did they calculate $c(x)...
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Why was Rijndael the only cipher to have a variable number of rounds?

Rijndael was the only AES candidate which defined a different number of rounds for their 128, 192, and 256-bit versions (10, 12, and 14, respectively). The others had a fixed number of rounds (32 for ...
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Generation of Rijndael S-box [duplicate]

I'm an electrical engineering student and was doing a brief research regarding the round transformations of the AES-128 and came across the Wikipedia article describing the generation of the ...
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Security analysis of Rijndael (AES)

I was studying the Rijndael Block Cipher for an assignment. I am looking for a (layman-ish) explanation as to why the cipher is secure. Googling did not seem to be give any good explanations. The ...
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Need help understanding math behind Rijndael S-Box

in Rijndael SubBytes() step all bytes of input block are substituted based on a lookup table S-Box. S-Box is initialized by taking all elements of $GF(2^8)$, ...
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32bit AES equals to 8bit AES?

I am looking into an article about 32bit CPU/MCU software implementation of AES and there are some weird changes over there. Like shift-rows. It seems that the shift-rows in the 32bit implementation ...
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Why are polynomials chosen with coefficients in $GF(2^{8})$ in Section 4.3 of NIST FIPS 197 for implementing AES?

I was trying to understand AES (Rijndael) from a very mathematical perspective. I'm quite new to abstract algebra and Galois Fields. I understood that we are considering a byte (8 bits) as a ...
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Clarification on polynomial used in Rijndael MixColumns implementation

I'm seeing the fundamental function in open source code for Rijndael MixColumns implementation. (Picture below) If i translate the 8'h1b correctly, it is represent the polynomial of $x^4+x^3+x+1$. ...
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AES S-box and Nothing Up My Sleeve

Cryptographic primitives should have nothing-up-my-sleeve property to prove their designers don't have an advantage in using them versus the general public. For example, Blowfish is using binary ...
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Why are AES keys increments of 64-bits?

Why are AES keys increments of 64-bits? Rijndael, which subsequently became AES, allowed key increments in 32-bits (128, 160, 192, 224, and 256 bits). However, AES made it 128, 192, or 256. My guess ...
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What are easy yet fool proof ways of ensuring that AES encryption algorithm works like it should and no bugs/developer mistakes have sneaked in?

As a developer when it comes to encryption, there is an insane amount of weakness/mistakes/bugs that the programmer can add to the encryption algorithm. So a pretty general question to the crypto pro’...
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Which character / byte to use to divide AES ciphertext into chuncks?

I am implementing a cross platform AES cipher. Everything works fine except for super large file, those I encrypt by for example taking first 1kb of the file generating a cipher message (all chunks ...
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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 ${\displaystyle \operatorname {GF} (2^{8})} $. ...
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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 ...
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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 ...
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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 = ...
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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 ...
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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 ...
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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: ...
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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 ...
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How can the Rijndael SBox be written as a linearized polynomial?

In Cryptanalysis of Block Ciphers with Overdefined Systems of Equations Nicolas Courtois and Josef Pieprzyk state (in Appendix A) that the Rijndael SBox can be written as a "linearized polynomial" $S(...
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Who said "32 round Rijndael" in the third AES Conference

This is a historical question. In the third AES Conference of NIST (AES3), April 13-14, 2000, New York, near the end of the conference, one representative for each of the last 5 candidates sit on a ...
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Risks using .NET RijndaelManaged with static Key and IV

A company I'm consulting for has a (quite old) home grown web SSO solution based on an encrypted cookie. The auth flow looks more or less like this: User hits protected page on integrated site Site ...
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Is Rfc2898DeriveBytes random? C#

I am trying to wrap my head around encryption in .NET. I am trying to implement a simple solution in ASP.NET Core to encrypt a cookie containing some non-meaningful numbers to outsiders. I need to be ...
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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, ...
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AES S-box input and output question

I am new to cryptography. I am looking to understand how to answer this question from my class: Find below the S-box of AES. Given the input 01010011 in binary, calculate the output.
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Replacing a block cipher's key schedule with a stream cipher

Take Rijndael (AES) of block size 128 and reformulate it with a tweakable number of rounds and no key schedule. Suppose we obtain: Rijndael128(r, k) where r is ...
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How to find the right additive polynomial in inverse affine transformation in AES

Addition polynomial affine transformation rijndael is (x^7 + x^6 + x^2 + x) The affine transformation represented in A(x) A(x) = (x^7 + x^6 + x^2 + x) + a(x)(x^7 + x^6 + x^5 + x^4 + 1)mod x^8 + 1 ...
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AES S-Box implementation: from a byte-by-byte to 2-bytes-by-2bytes?

The S-Box in AES encryption is a byte substitution step. Is it possible to perform the substitution 2 bytes at a time, rather than 1 byte? What are the challenges/trade-offs involved?
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AES key expansion for 192-bit

In AES-192 key expansion there are 12 rounds and 52 keys. I am not sure why 52 keys are derived since each block consist of 4 rows and 6 columns (192 bit keys). So if the block is 4 x 4 then we ...
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AES - Finite Field Multiplication on 8 Bit Platform

Section 4.1.1 "Finite Field Multiplication"(page 53) of "The Design of Rijndael", it states How the equation 4.1 has been formed and transformed into equation 4.2? In section 2.1.6 "Polynomials ...
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AES Mix Column Transformation

Section 3.4.3 "The MixColumns Step"(page 39) of "The Design of Rijndael", it states The columns of the state are considered as polynomials over $\operatorname{GF}(2^8)$ and multiplied modulo $x^4 ...
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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. ...
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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 ...
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Node.js/OpenSSL crypto library equivalent of a Rijndael implementation

I have a Rijndael function that I've implemented as a JavaScript port of a C reference implementation in a technical specification for the MILENAGE algorithm (ETSI TS 135 206 V14.0.0 (2017-04)). My ...
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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 ...
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2 votes
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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 ...
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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 ...
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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 ...
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How are Rijndael's S-Boxes generated?

Wikipedia: Rijndael's Forward S-box I'm writing C Code to generate S-boxes but I'm stuck. Would you mind explaining one entry of the S-box? (say for x = 0x2). ...
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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 ...
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How 2 rounds in AES achieve full diffusion?

I have read somewhere that 2 rounds is AES provide full diffusion. So I looked it up to find out what it exactly meant. In The Design of Rijndael page 41, section 3.5 and it states that: Two ...
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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?
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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 ...
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13 votes
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Is there any compelling or logical reason to use AES-192 over AES-128 but not use AES-256?

I have been trying to find a case where AES-192 is used over AES-128 but AES-256 is not used. There are many questions about AES here (I liked this one AES-128/192/256), but from the actual ...
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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 ...
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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 ...
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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 ...
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