# All Questions

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### Identity-Based Encryption consist of four algorithms. Extract phase is one of them and it is done by PKG or receiver?

The Identity-Based Encryption consist of four randomized algorithms: Setup, Extract, Encrypt, Decryption. The Setup phase is done by Private-key generator, Encrypt by sender and Decryption by ...
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### Are passwords generated from sine vulnerable to certain attacks?

A friend mentioned that he used the sine of a number, i.e. sind(54), to generate long passwords. This way he only has to remember sine 54 and have a calculator to get his password back. I am wondering ...
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### Simple multiplication as an encryption method

There was a time when I wondered about multiplication as an encryption operation. That was when I was thinking in terms of modular multiplication. But how about based around simple multiplication. ...
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### OpenSSL encrypted text length

OpenSSL block ciphers return length of the text as output of the encryption (envelope_seal()), and If I have to send the length over network, I append the length ...
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### Noisiest RF band for random number generation

I've been looking into the difference between PRNGs and proper RNG techniques. One that I particularly like is the idea of tuning a radio to a certain frequency and bandwidth and just listening to the ...
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### Client-Server application how can data be encrypted so only clients can read it

Requirements We are building a system that connects multiple clients through a restful API. It allows the creation of groups of trusted clients. We need a way to store group shared data encrypted ...
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### Counter Mode with a sequence of zeros bits plaintext, is it secure?

I had a quiz last week in computer security course. There was a confusing question that I am still looking for a good and clear answer. First, I know that counter mode with a good block cipher is ...
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### RSA generation of private key using public key

In RSA private key generation e*d ≡ 1 mod φ e is public, also n is public. How to prove mathematically, generation of ...
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### CPA security of a stateless and deterministic encryption system

Why can no stateless and deterministic encryption system be IND-CPA secure? Is there a formal proof for it?
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### Proof that $gcd(e, \lambda(N)) = 1 \hspace{1mm} \Longleftrightarrow \hspace{1mm} gcd(e, \varphi(N)) = 1$

What is the proof for the fact that $gcd(e, \lambda(N)) = 1 \hspace{1mm} \Longleftrightarrow \hspace{1mm} gcd(e, \varphi(N)) = 1$ Where: $N = P * Q$ where $P$ and $Q$ are both primes. $\varphi(N)$ ...
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### Applications of GF(p) polynomials

A Galois field of the type $GF(p)$, where $p$ is prime, is normally expressed as the ring of integers modulo $p$. If my understanding is correct, it is also possible to represent its elements as a ...
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### Is there a strong cryptographic reason for GCM's 2^39 - 256 bit limit?

In reading through the original GCM specification (McGrew & Viega '05), the composition of the 128 bit Initialization Vector as a concatenation of a 96b nonce and a 32b unsigned wrapping counter ...
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### How much work is required to detect multiple collisions for a hash function?

Assume an ideal hash function of output size n bits, detecting one collision requires approximately 2^(n/2) evaluations of the ...
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### display an image encrypted with ECB [closed]

On wikipedia there is an example of a picture encrypted with ECB: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Electronic_codebook_.28ECB.29 I just wanted to know how an encrypted ...
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### How does RSA padding work exactly?

I've read everywhere online and people say plain text RSA is very unsafe. To make it safe you pad it but no examples are shown anywhere on how to do it. It's explained that random data is added to the ...
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### Why can't I use ECB with some obfuscation for transient RAM?

I understand that ECB does not hide data patterns well. But my understanding is that it cannot be broken to "know" the underlying message. If that was the case, why can't ECB be used with some ...
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### RSA signing security

I'm curious about the security of RSA signing with the same public private key pair when the same message is sent multiple times. It's my understanding that once you generate the hash of the message ...
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### Automated testing of cipher security for import/export compliance [closed]

What do we know about systems that automatically test and grade cipher security. The application in mind would be for checking for compliance with import/export regulations. I imagine a system that ...
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### Integrity protection in wireless sensor networks [closed]

I have done a lab about wireless sensor nodes and got in touch with encryption for the very first time. There are some questions on my sheet, especially on integrity protection (the attacker wants to ...
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### Where are the ChaCha20 test vectors/examples?

I see in the Salsa20 specification there are test examples throughout the document to help an implementer make sure every function works as designed. Consequently the whole algorithm would work ...
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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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### 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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### Is a Combined Linear Congruential Generator secure for cryptography? [closed]

I learnt that a Combined Linear Congruential Generator (cLCG) has better properties than a Linear Congruential Generator (LCG). For those who don't know what a cLCG is, here are three links that might ...
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### what is it called when encrypt('a') + encrypt('a') == encrypt('aa')?

So normally if you do encrypt('a') twice in a row you'll get the same result. But sometimes (as is the case in SSH) this is not desirable. You want encrypt('a') + encrypt('a') == encrypt('aa'). What ...
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### How to use HMAC for authenticating multiple messages

The standard HMAC function, $H(K, m)$, authenticates a single message $m$. Instead, I'd like to authenticate 2 messages, like this: $$H'(K, m_1, m_2)$$ The simplest solution, $H(K, m_1||m_2)$, ...
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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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