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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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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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1answer
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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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1answer
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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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1answer
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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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869 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 ...
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1answer
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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 ...
4
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1answer
473 views

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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1answer
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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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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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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 ...
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AES standard C library implementation

I'm working to implement AES (128/256 - either) on one of the RISCV ISA processors & later improve performance by introducing a custom instruction in RISCV ISA. I'm a crypto newbie and plan to ...
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1answer
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How to perform the modular reduce of Rijndael's finite field

I am trying to understand how to calculate the modular reduction of Rijndael's finite field. The example on this page says that {53} • {CA} = {01}, because ...
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Is there a way to cleanse a picture of information from steghide?

Recently I learned of the steghide application (a command-line tool allowing the use of steganography, the art of hiding information inside other information, used in practice with JGP and WAV files ...
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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 ...
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1answer
442 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 ...
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1answer
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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....
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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 ...
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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 ...
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1answer
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How do Käsper and Schwabe's Bitsliced AES Mixcolumns work?

The only way I see it possible to do the matrix-multiplication in the MixColumns operation of AES is by shifting the bits in the multiplied number, and then reduce with the polynomial if needed. ...
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What is the fastest block cipher in the (Intel) world?

In AES competition,Rijndael cipher obtained first rank and become Standard and Serpent, Twofish, RC6 and MARS obtained another ranks and I know that Serpent took second rank because it was slower than ...
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AES - Size of T-Boxes and obtaining T-Box values

In article "A high performance ST-Box based unified AES encryption/decryption architecture on FPGA" (http://www.sciencedirect.com/science/article/pii/S0141933115001945) two 32Kb dual-port BRAMs are ...
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For what does “Rcon” stand for in Rijndael/AES?

How do we expand the abbreviation “Rcon” used in the Rijndael key schedule? I know what it is, I know how it works; I just do not know for what it is a shortcut for. I mean: if "Sbox" is "...
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2answers
581 views

Help with breaking AES reduced to 2 rounds

I was studying Rijndael AES proposal, and its cryptanalysis. I started with writing code to break AES reduced to 2 rounds. I am using 128 bit key size and 128 bit block size. 2 round AES means the ...