# Tagged Questions

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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### Why is Rijndael key length restricted?

Why is Rijndael restricted to key length in {128, 160, 192, 224, 256} bits (and not larger)? The algorithm looks to me like it would support an arbitrary-sized key (multiple of 32). The rounds ...
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### Found a way to crack AES-128, what now?

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 DES and other ciphers but how did they ...
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### How can I calculate the Rijndael SBox?

I would like to implement the Rijndael subBytes() operation using calculation instead of tables, because I like to play with this on different wordsizes, as an ...
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### Choice of multiplication polynomial in Rijndael s-box affine mapping

The Rijndael specification details the design choices for the s-box in section 7.2. They describe the choice of affine mapping as follows: We have chosen an affine mapping that has a very simple ...
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### How can I find the multiplicative inverse in the first transformation of the SubBytes() transformation in AES?

In FIPS-197 §5.1.1 , it says the first transformation in the SubBytes() transformation is: Take the multiplicative inverse in the finite field $\text{GF}(2^8)$ described in Sec. 4.2; the ...
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### About the Rijndael/AES sbox polynomial (subBytes)

I've recently read a question about the irreducible polynomial behind the subBytes() operation in the Rijndael that has awakened and old curiosity I have: Why $\,m(x)$ was chosen as ...
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### IV = Filename XOR CipherKey?

i want to encrypt transparently using Rijndael. So this is, what I thought of and I would like to have an opinion from "Experts" whether this will harm encryption strenght. I am using chunks of 1MB ...
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### a doubt in Rijndael's key expansion sizes

I've often heard/read that AES key sizes 256 & 192 would be weaker than 128 or not stronger as expected from the size increase, but I've never seen a proof. How does one proof the strength of a ...
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### Choice of reduction polynomial in Whirlpool's internal cipher

Whirlpool is an interesting little hash function in the Miyaguchi-Preneel family. In my mind, it's most interesting feature is the design of internal cipher W, where the distinction between key and ...
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### Does the key schedule function need to be a one-way function?

For some key schedule $e_n(e_{n-1}(k))$ (where $e_{n-1}(k)$ is the result of the previous round) , does $e$ need to be a one-way function? In the case of DES or Rijndael the key schedule doesn't ...
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### What is “serial concatenation”? [closed]

I have a third-party point-of-sale API (Speedflow Pay-N-Get) that I am trying to communicate with over HTTP, but I have a problem with it. In a nutshell, a request is encrypted using RSA, and the ...
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### Rijndael: explanation of Rcon on Wikipedia?

I stumbled onto the explanation of Rijndael Rcon on Wikipedia, and I can't follow it. The example for Rcon indicates that Rcon(9) is 0x1b. That could make sense… ...
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### Where is the S-Box generated in Rijandel/AES?

It's rather kind of lame questions, and I can't find good and clear explanation: In which step of Rijandel is S-box generated? Is the S-box reused in every round of cipher or is generated in every ...
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### Using IV buffer after altered inside a Rijndael CBC Encryption/Decryption process as IV for next message?

When sending a block to be decrypted or encrypted, with RijndaelCBC, we input the data to decrypt/encrypt and an IV for syncing and to prevent identical outputs for identical inputs. This question is ...
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### AES key expansion: 256bit key

In AES algorithm, in the key schedule, Why does the expansion of a 256 bit key need an extra application of the S-box, unlike the expansion of 128 bit and 192 bit keys ? (The obvious answer would be ...
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### AES ENCRYPTION ALGORITHM [closed]

What is the amount of decrease in the probability of decrypting a data encrypted using an AES algorithm? (That is by introducing each round out of ten whole rounds, how the probability of decryption ...
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### Why does Rijndael with a 256-bit block require the bottom two rows to be shifted one more space than usual?

From Wikipedia: For a 256-bit block, the first row is unchanged and the shifting for the second, third and fourth row is 1 byte, 3 bytes and 4 bytes respectively. Why the change? Is there any ...
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### Difference between Rijndael 128 / 256 blocksize implementations? (and impact of block size in general)

Can anyone shed some light onto the advantages/disadvantages of using Rijndael with 256-bit block size, as opposed to the 128-bit (AES) implementation? (please note: I'm not referring to key-size ...
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### NIST Standard for Advanced Encryption Standard Algorithm [duplicate]

Possible Duplicate: Advantage of AES(Rijndael) over Twofish and Serpent What is the reason of NIST why Rijndael choose as the Advanced Encryption Standard
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### Advantage of AES(Rijndael) over Twofish and Serpent

I'm trying to figure out a suitable encryption technique and after reading a bit, I figured the current AES 128-bit encryption is suitable for what I'm trying to do. However, this is more due to the ...
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### What is the complexity of the Square attack against the reduced 4-rounds 128-bit Rijndael variant?

I'm looking at a square attack against a reduced version of AES-128 with only 4 rounds (with block and key size of each 128 bit). I have a set of 256 plaintext-ciphertext block pairs. What is the ...
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### Storage of Private Keys

I'm building a bitcoin web application that will require all users to be assigned a wallet for adding funds to their account. I plan on exposing the public key to the user (the bitcoin address). Users ...
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### What is the difference between these AES encryption methods

I am using AES encryption (Rijindael) with Base-64 encoding in Obj-C and VB. I am currently using the following two projects to achieve this: Obj-C: ...