# All Questions

18,380 questions
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### Is forward secrecy overhyped or necessary?

Forward Secrecy, also perfect forward secrecy, gives assurance about session keys even the private key is compromised. This is achieved by generating a random key per session without using a ...
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### Is simple EC arithmetics enough to construct security proofs?

Using the simple rules of modular arithmetics for Elliptic Curves, including associative and commutative rules for $+$ and $*$, where uppercase letters are points and lowercase are scalars on the ...
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### Method for generating random number(s) [closed]

I was reading about random numbers and their usage in security. I'd like to verify with more experienced people how good this method of generating random numbers will be. Human beings are very hard ...
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### Offline Group Key Agreement - Cross Device Syncing

I have a specific use case I am interested in. I have spent the better part of the night reading research papers. I am beginning to believe what I want is not possible so I wanted to confirm here. ...
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### What is the difference between Forgery and Chosen-Message Attacks?

I did some researches about forgery attack and chosen-message attack. For me, forgery attacks are more focused on the verifiability whereas chosen-message attacks are similar to brute-force attacks. ...
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### Niederreiter cryptosystem

I can't understand how Niederreiter cryptosystem works. If $c=mH^{'T}$ than why we cannot compute $m$ directly by multiplying $c$ with the $(H^{'T})^{-1}$? Can you give me an example of a "fast ...
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### Is LibreSSL affected? - Downgrade Attack on TLS 1.3

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Google made the headlines with its new Adiantum encryption method, and i read (TechCrunch) that: In the meantime don’t expect any instant gains, but future low-power devices may offer better ...
55 views

### Is RSA in decline across the board?

From what I gather from the internet (source), the recommended practice for 2019 and beyond is to avoid RSA and use ECDH and ECDSA. Is this the general case?
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### Is a hash more or just equally representative of the first [hashlength] bytes of the hashed one-time pad?

[Clarification edit further down.] To distinguish already existing one-time pad files by their content instead of just their name ... ... is hashing meaningful? Or would the first X bytes (Length ...
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### To get 128-bit security for RSA, the modulus should be 4096 bits. How was that determined? [duplicate]

My understanding of security level is that for a crypto scheme to have n-bit security means it would take $2^n$ operations to break it. For something like AES with a 128-bit key, it's straight-...
5k views

### Is one-time pad encryption vulnerable when near identical data is sent many times with different OTP?

Let's assume a text file that grows at its very end but is otherwise not edited. We now have 100 transmissions of this, but OTP-encrypted (different OTP each time, of course). The first 50% of the ...
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### Using key derived using HKDF or NIST sp800-108 with AES-CCM/GCM

Is it safe to use keys derived using HKDF or NIST sp800-108 with AES-CCM/GCM ? The NIST SP800-108 and SP*00-56C spec says "To comply with this Recommendation, the derived keying material shall not be ...
319 views

### Encrypting between nodes that have RSA keys: Diffie-Hellman or random secret key?

I have two peers with RSA keys; they want to encrypt a non-trivially sized message between them, so I want a random AES symmetric secret key, which is encrypted with Bob's public RSA key, and sent ...
44 views

### If I hash ABC123, where ABC123 appears five times inside the file, will each of the five instances of ABC123 appear as identical hash values? [closed]

If I hash the word SOUND, where the word SOUND appears five times inside the file, will each of the five instances of SOUND appear as identical hash values?
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### Storing passwords in a publicly available database

I have a public database where users need to store configuration files. The file can contain passwords. Everyone can read config files but only the server can read passwords in them. In the browser, ...
55 views

### Participant workflow in the Cryptography competitions [closed]

I learned about the NIST hash function competition which generated SHA3. It says it inspired a Password hashing competition too, which resulted in Argon2. What I'm wondering is what people generally ...
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### Finding $P$ when we know $2\times P$ in given Elliptic Curve [duplicate]

For a given elliptic curve $E$ like this $y^2 = x^3 + Ax + B \pmod p$, can we find the point $P$ if we know that the $Q = 2\times P = (a, b)$? For example $E:\ y^2 = x^3 + x + 1 \pmod {10007}$, we ...
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### How can I verify certificate signature algorithm in TLS 1.3 using PSS?

I've read this post but I'm still unable to understand some things. I'm trying to verify that the signature algorithm used in the certificate matches the proposed list from the client. (As it's ...
72 views

### Original papers for hashing functions

I would like to learn how hashing functions are discovered / created. In part of this process I think it would be helpful to see the original works or papers of any authors of cryptographic or non-...
43 views

### Adding new share (Shamir Secret Shares ) [duplicate]

I am using this https://github.com/gburca/ssss-js Shamir implementation. I generated 4 shares from secret (threshold of 2). I am wondering if I can recreate (interpolate) original polynomial from ...
49 views

### What is the purpose of an Authentication Tag in AEAD encryption schemes?

AEAD encryption schemes produce something referred to as an "authentication tag." What does this tag consist of, what is its purpose, and is the tag itself human-readable data such as a plaintext ...
24 views

### Witness-Extended Emulation

I am reading up on Sonic: Zero Knowledge SNARKS from Linear - Sized Universal And Updateable Structured Reference Strings. An excerpt: For soundness, we do not use the standard definition of ...
39 views

### How to identify RSASSA-PSS from rsaEncryption OID?

Following the RFC 8446 it states that: RSASSA-PSS RSAE algorithms: Indicates a signature algorithm using RSASSA-PSS [RFC8017] with mask generation function 1. The digest used in ...
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I am trying to solve this question and I have no idea how to find the value for $q$. I know that I am supposed to find the probability of $q>3q/512$ in terms of the equation $q$, but not sure how? ...
42 views

### What does 2-flat mean when discussing APN permutations?

I am currently reading a research paper that uses the term 2-flat. However, I don't understand what this term means. For example, the paper mentions in its definition of APN that for all distinct $a$,...
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### The meaning of formal and semi-formal in cryptography

The question is about "formal" analysis, proofs, etc... What is a correct definition of a formal proof, or a formal analysis? Is there a good way and a bad way to formally prove something. What is the ...
153 views

### Diffie-Hellman private key recover with non-prime modulus

Say we have a classic Diffie-Hellman key exchange. We have the following parameters of a public key: p,g,y Where $p$ is the modulus, $g$ is the base, $y$ is the ...
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### Distinguishing generators of RSA primes and moduli

We are trying to distinguish two RSA prime generators: Prime generator 1 draw uniformly at random an integer $p$ with $2^{1023.5}<p<2^{1024}$, until it is prime output $p$. Prime generator 2 ...
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### Mitigating leakage of asymmetric encryption scheme leaking the length of plaintext

Asymmetric encryption schemes do leak something about the encrypted plaintext: the length of the plaintext. How can this be mitigated? My solution: Padding the plaintext with some string of the ...
24 views

### How the ciphertext generated within a CP-ABE scheme is structured?

In ciphertext policy attribute based encryption 1 we use a tree structure with different keys into order to access attributes and the attributes are embedded to the ciphertext. Could you please let ...
101 views

### How to change hash checksum of a text file without changing the contents in the file

I have created a text file called test.txt and the content of the file is Hello World I would like to change the SHA checksum hash without modifying the contents and filename. Is there any way to do ...
52 views

### 1-digit MAC with error-catching properties?

The well-known Luhn check digit (used in credit-card numbers) is a public method to append a check digit on the right of a decimal number, so that any 1-digit alteration and any exchange of two (...