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### What are the general rules to follow if I want to design a block cipher suitable for file encryption? [duplicate]

Can you please tell me what should be the quality of an encryption function using a key size of 256 bits... I realized from my previous question that a simple XOR of plaintext (256 bits) with a ...
31 views

### What are some good softwares to help create block ciphers? [duplicate]

I'm working on my own unnamed block cipher currently. It uses permutation networks, rotations (bitwise and quitwise) and bitwise operators. Are there any good softwares and/or libraries to program in ...
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### Check linear and differential cryptanalysis of a new block cipher [duplicate]

I am developing a new block cipher primitive. I would like to test its robustness against attacks of linear and differential cryptanalysis. Is there a tool to evaluate this using only plaintext and ...
7k views

### Reason why “XOR” is a linear operation, but ordinary “addition” isn’t?

I'm new in cryptography and try to read some articles in this field. Many of these articles talk about non-linear S-boxes, and nothing more on what they mean by their non-linearity. I have a simple ...
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### Why do block ciphers need a non-linear component (like an S-box)?

Why is there a requirement of "Non-Linear functions" as a component of many popular block ciphers (e.g. the S-box in DES or 3DES)? How does it make the cipher more secure? The only intuition I have ...
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### Can you explain “weak keys” for DES?

A weak key for DES is a key $K$ such that $DES_{k_1}(DES_{k_2}(x))=x$ for all $x$. I don't get why are the 4 keys $k_1||k_2$: $1^{112}$, $0^{112}$, $0^{56}||1^{56}$, $1^{56}||0^{56}$ considered as ...
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### Why are bitwise rotations used in cryptography?

Any understanding I have of cryptography stops right around the cipher level. As such, I'm just curious as to why bit shifts and moreover circular bit shift are so prevalent in cryptography.
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### What does Maj and Ch mean in SHA-256 algorithm?

I'm guessing they're some kind of standard function but what do they do and what do the names mean? A little explaination or link me to an article would be great.
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### What are the requirements of a key schedule?

In the first block cipher I designed I used a CSPRNG to generate the round keys. The purpose was to at least have a chance of creating a (hopefully!) secure cipher on the first try (but please don't ...
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### What are the qualities of a good block cipher? Beginner, Intermediate, Advanced, Expert [closed]

Notice: I'm doing this to learn. I know not to use a homemade cipher for anything that requires security. I also have heard before I'm not supposed to be trying this, but I learn best through trying ...
2k views

I was looking at the algorithm for Twofish, and I noticed that in some places a XOR is used, but in others, they use "addition modulo-32." What makes modulo-32 special? Why not always use XOR? Why not ...
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### AES timing attacks

I'm just interested in cryptography, so please don't expect me to be an expert. ;) I recently read about AES cache timing attacks and found it very interesting. I read the article Cache-timing attacks ...
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### How does ROTL work?

what does ROTL stand for? I know it does left shifting but what about the acronym? When we do a left shift, do we take the leftmost bit and add it at the end, by making the second bit the first, and ...