# All Questions

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### How to implement the Salsa20 hash function?

I am currently implementing Salsa20 from the specification as an exercise in learning and self-flagellation. I have Sections 1-7 passing the test examples provided. I am now stuck on Section 8, The ...
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### Discrepancy with reported key size for EDE ciphers in Qualys SSL Labs

The following two cipher suites were reported by Qualys SSL Labs as being 112-bit: SSL_CK_DES_192_EDE3_CBC_WITH_MD5 TLS_RSA_WITH_3DES_EDE_CBC_SHA However, all other references I can find say that ...
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### Hardness of problem related to bilinear pairings

Let $e: \mathbb G_1 \times \mathbb G_1 \rightarrow \mathbb G_T$ be an efficient bilinear pairing. Note that the pairing is symmetric (i.e., Type 1). The problem is, given $g \in \mathbb G_1$ and ...
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### What is a good way to demonstrate elliptic curve cryptography?

For school (high school) I am writing an essay on elliptic curve cryptography. The assignment needs to include a practical part, so I decided to write a Python class for elliptic curves. This class is ...
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### Is my method symmetric encryption?

To obfuscate data I made up this method on the spot without planning since the goal wasn't real encryption. At first I though this cannot be real encryption but after revisiting the code and reading ...
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### Prime Numbers in Discrete Log

I am implementing a security protocol based on discrete log. I came across the equation $p = kq + 1$. Understand that based on number theories that both $p$ and $q$ should be large enough to be ...
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### Post-quantum hybrid encryption

Assume the following simplified protocol: seed = curve25519SharedKey(theirPublicKey, myPrivateKey) sharedKey = scrypt(seed, salt, sufficientlyHardWorkFactors...) cipherText = aes256(sharedKey, ...
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### “Kernel attack” on MinRank — why do we guess $\left\lceil \frac k n \right\rceil$ vectors?

The kernel attack on MinRank is described here (page 5). My question refers to this line: Note that if $m = \left\lceil \frac k n \right\rceil$, the system essentially has only one solution ...
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### What would be the best plain text Cryptography method without the use of a computer? [closed]

What would be the best Cryptography method without the use of a computer? This could be a list of the current options available, that could be used without the use of a computer ...
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### Looking for a secure PRNG that I can implement in hardware

I'm trying to implement a (sort of) simple PRNG in hardware for fun. My idea would be to allow a user to enter a key using a keypad (or some dip switch settings that can be set and hidden) and to ...
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### What are the potential (major) flaws in this security scheme?

It’s been a few years since I read anything involving crypto. I’ve come across this scheme and I wonder how secure it is: Alice generates an RSA keypair (we assume Alice is using proper random ...
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### rotational cryptanalysis on modulo multiplication?

I saw the paper 'Rotational Cryptanalysis of ARX', it is effective against design primitives using XOR, addition, and rotation. http://www.iacr.org/archive/fse2010/61470339/61470339.pdf However ...
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### Proving the semantic security of the One Time pad

Currently hearing a lecture on cryptography, and the professor gave us the definition of semantic security, which is roughly the following (formally not quite complete, but you get the idea): ...
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### RSA: Fermat-Euler Theorem - coprimality of message and modulus [duplicate]

I understand the implication of the Fermat-Euler theorem and how it applies to RSA and the detailed explanation by user Ninefingers at What is the relation between RSA & Fermat's little ...
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### Available programs that can verify the working of a simple substitution cipher

Is there any tool available that can test whether a simple substitution cipher is working. I will put my scenario in detail. Lets say I built a simple substitution cipher that maps 8 bit data to 16 ...
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### Repeated XOR decryption [closed]

I have this message in Hex: ...
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### In RSA, why does Alice's $N$ need to be relatively prime to Bob's $N$?

I was asked this by my professor and I didn't understand the reasoning behind it. If Alice has a the key pair $(p_a, n_a)$ and Bob has the key pair $(p_b, n_b)$, why do $n_a$ and $n_b$ have to be ...
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### Complexity of preimage resistance

Why is the complexity of pre-image resistance $2$ raised to the power of $n$? I have been looking in everything lecture about pre-image resistance, but I still didn't know the answer.
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### Why develop new stream ciphers when block ciphers can be trivally made into streams?

I've just been reading about a new drop-in replacement for the RC4 stream cipher, but why develop new stream ciphers when AES can be made into a stream with a little XORing?
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### Direct sum of Binary numbers In Mixcolumns

I have just started learning cryptography and I am trying to make sense of the direct sum on some binary numbers. I am trying to find a column of a state space after a Mixcolumns operation has been ...
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