# All Questions

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### What is the difference between MAC and HMAC?

In reference to this question, what are the "stronger security properties" that HMAC provides over MAC. I got that MAC requires an IV whereas HMAC doesn't. I also understood that MAC may reveal ...
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### Encryption algorithms larger than 256 Bit for “big data” encryption?

I'm somewhat new to encryption. When looking at encryption programs for big data, I frequently see a maximum of 256 bits. Why do we generally restrict our (symmetric) keys to 256 bits? Can more ...
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### Why should I make my cipher public?

As I understand it, the less people know about the internals of my protocol or cipher, the more secure the protocol is. However Kerckhoffs's principle states that A cryptosystem should be secure ...
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### Are there any paper/human strong crypto systems? [duplicate]

Are there any paper/human executed crypto systems that have reasonable strength? I am aware of a few candidates so far Solitare from Cryptonomicon https://en.wikipedia.org/wiki/Solitaire_(cipher) ...
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### What are the practical implications of ciphertext distinguishability?

Commonly there are four ways to "break" a secrecy-focused cryptosystem: Recover the secret key Recover the message Distinguish an encryption from random noise Distinguish the encryption of two ...
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### One time pad ciphers in emails

In order to achieve very high security for privacy, would it be cryptographically secure to use one time pad ciphers in emails? The distribution of the keyword would pose no problems since I would ...
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What is the advantage of AEAD ciphers? Why is the TLS working group pushing for them? I thought modern cipher suites require SHA256 for authentication. What advantage is there to including Poly1305?
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### Point addition in NaCl/libsodium (Curve25519)

In NaCl and libsodium, the crypto_scalarmult function implements the operation $Q = kP$ (scalar/point multiplication). There doesn't seem to be a function for point ...
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### What if the p and q used in keys generation of Pailler cryptosystem are composite?

I've seen a few implementations of Paillier cryptosystem that uses probable primes to choose $p$ and $q$. Assuming that a keypair is generated with $p$ and $q$ that are coprime and that $pq$ is ...
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### What is the definition of “the correlation” and “the difference propagation probability”? [on hold]

Non linearity has two properties: 1. the correlation 2. the difference propagation probability what is the definition of each concept?
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### parallel shifters [closed]

suppose there is two registers each of size 8 bit and the inputs to these register are in parallel so can we combine this 2 register so that new combined register will have input 16 bits and all are ...
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### how can eve guess a pseudo-random key has been used for encryption [on hold]

I am stuck in my project and earnestly need suggestions for the above question
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### AES-CTR with ephemeral keys vs IV

Let's say that we have a key exchange of some sort, which leaves A and B sharing the long-term secret $S$. Then, A and B want to use AES-CTR for the communication, which leaves us with several ...
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### Attacks on elliptic-curve based cryptosystems through solving the Decisional Diffie-Hellman Problem with the Weil Pairing

Are there any examples of practical attacks on cryptosystems set over elliptic curves which utilize the easiness of DDH for certain choices of curves $E(\textbf{F}_q)$, and as such their lack of ...
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### Light weight crypto library implementations [migrated]

Are there any open source crypto libraries that can be used in embedded systems or in other memory constrained places like a boot rom? I am looking for libraries that I can compile only the algorithms ...
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### Basic cryptography [on hold]

{First of all I'd like to apologise about my English} I'm interested in most popular cryptography encodements, but ones, where the substitution cipher is known (for example Caesar's code), not created ...
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### PGP String to Key specifiers

I've been reading through the PGP Standard and here I'm a little confused. This section is discussing converting string data to a session key. I'm confused about the paragraph in bold. First off, what ...
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### Example: pre-image resistance to second pre-image resistance

It is possible to convert a pre-image resistant function $f:\{0,1\}^{n}\rightarrow \{0,1\}^{n}$ to a second-preimage resistant function? I am thinking to use a pseudo-random generator and construct ...
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### What consequences do the plaintext space size has on the performances in the BGV scheme?

In the BGV paper [1], the authors say in §5.4 that you can have $\mathbb{Z}_p$ as plaintext size with a large $p$. What is the impact of the size of $p$ on the ciphertext size and computational work ...
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### Help me find out what type of encryption this is. [on hold]

Alright this may not be an easy one. May not be something anyone knows. What I do know already (and I have made a password recovery tool from what I have learned) The password is translated into a ...
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### need help for decrypting a cipher.. i am new to this so was wondering if someone could tell me how to go about it [on hold]

how to begin to decrypt any numeric cypher? what are the basic steps to solve easy numeric cyphers?
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### Is there any such thing as “proof of location”?

I'm looking for a way for someone to prove to me their geographical location without a trusted third-party. Imagine wanting to prove to someone you're actually physically in a specific place. I'd ...
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### Why calculate pi to estimate randomness?

Why do testing suites calculate pi using the Monte Carlo method to determine if a series of numbers are random? As far as I can tell, the Monte Carlo method can be used to estimate pi itself (as a ...
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### I don't know whattype of cipher this is [on hold]

I am trying to solve the following sipher Nosdhiibotidcylhrdeovedljuetre I have no experience with ciphers but substitution didn't seem to work, and since its a long string without breaks process of ...
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