Questions tagged [rsa]

an asymmetric (e.g. public-key) cryptosystem, based on modular exponentiation with big exponents and modulus. RSA can be used both for signature and encryption.

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Manually (mathematically) signing and verifiying a file using RSA [Solved] [closed]

It is only recently that I entered cyber security field.. and one of the main foundations is nothing but Cryptography. Something which always fascinated me was the 'Chain of Trust' which is holding on ...
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RSA Modulus doesn't match the primes [on hold]

I generated a 2048-bit RSA key with ssh-keygen. When running: openssl rsa -in key -noout -text The result is: ...
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Potential Coppersmith's attack on RSA

Sorry if I don't express myself well in English. The solutions $h$ and $k$ of $$[(h+1)^2]*[(2*h+2)^2/2-1]=X* M$$ and $$[(k+1)^2]*[(2*k+2)^2/2-1]=Y*M$$ are such that each $M$ number divisible by $...
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Estonian e-voting, vote verification system

I believe I do understand the basics of how the Estonian e-voting system works, but I'm stuck at their vote verification system. In order to get the vote verified, a client needs to encrypt all of the ...
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Does RSA key transmit with OAEP insecure?

In the Key encapsulation article of Wikipedia, the RSA-KEM is described shortly, as follows; Generate a random element $1<m<n$ then drive your symmetric key by $M=\text{KDF}(m)$ Then compute ...
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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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SonarQube: Make sure that encrypting data is safe here. AES/GCM/NoPadding, RSA/ECB/PKCS1Padding [migrated]

I'm using: 1. RSA/ECB/PKCS1Padding 2. AES/GCM/NoPadding To encrypt my data in my Android (Java) application. At the documentation of SonarQube it states that: The Advanced Encryption Standard (AES)...
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What is Reverse Trapdoor Function?

In wikipedia on Digital_signature: but rather, the message to be signed is first hashed to produce a short digest, that is then padded to larger width comparable to N, then signed with the ...
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What is a method for hiding RSA prime values from .exe De-Compiling?

I've just been looking into RSA encryption with C++ and am wanting to make a program that can en/decrypt files of my own custom file extension. Obviously I need to choose two primes numbers (for my p ...
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Is modulus a prime number important for non-symmetric cryptology?

From this link Generation of a cyclic group of prime order we know how to generate a prime order group. This illustrates why a prime order group is important. But why is modulus a prime number ...
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Is it possible to check if a number is the product of two primes without factorizing it?

I have a large number which I suspect may be a private RSA key (although its size, at 613 bits, seems a bit unorthodox). I have started to run a factorization algorithm on it, and after a few hours ...
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Relationship between special RSA modulus and quadratic residue in CL (Camenisch-Lysyanskaya) signature

I'm studying the CL(Camenisch-Lysyanskaya) signature (A signature scheme with efficient protocol proposed by Camenisch-Lysyanskaya). However, I cannot understand ...
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Private evaluation public quick verification VDF

Does anyone know of any VDF, that can be calculated by someone holding some private key in t sequential steps and is quickly verifiable in exponentially reduced step by anyone using some public key ...
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RSA get d from q and exponent1 [closed]

From RSA. Assume you have: publicExponent e, prime2 q, and exponent1 dmod(p-1) How would one go about finding d, i.e. the private exponent?
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RSA Key Generation Parameters - public exponent, certainty, string-to-key count

I want to know what values are appropriate for the public exponent and certainty when generating an RSA Key (for example using Bouncy Castle RSAKeyGenerationParameters function). What is the ...
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Why does RSASSA-PSS produce different signature each time even if I use same salt and same message?

I understand that RSASSA-PSS is not deterministic. But I see that in message encoding, MGF and SHA functions are deterministic. So even if I keep default salt length, it produces different signature. ...
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How to find modulus from a RSA public key?

I am studying the RSA cryptosystem. The public key consists of $(n, e)$, the modulus (product of two large primes), and the encryption exponent. I want to separate the modulus $n$ and exponent $e$. A ...
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Why isn't semiprime encryption reversible? [closed]

I understand that semiprime encryption works by having private keys (prime factors) and public keys (semiprime), but what I don't see is how you can encrypt with a semiprime but not decrypt with it. ...
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Why Static RSA and Diffie-Hellman cipher suites have been removed in TLS 1.3?

Why Static RSA and Diffie-Hellman cipher suites have been removed in TLS 1.3? How keys can be exchanged then? https://tools.ietf.org/html/draft-ietf-tls-tls13-28
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Size of Key Material of TLS_DHE_RSA_WITH_AES_256_CBC_SHA

What is the size of key material required for generating MAC keys, encryption keys and IV when use TLS_DHE_RSA_WITH_AES_256_CBC_SHA ? How to calculate it?
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RSA PSS security advantage

To my humble opinion, please correct me if I'm wrong, RSA-PSS (PKCS#1 ver 2.1) advantage over RSA as described in PKCS#1 ver. 1.5 is in its security proofs. Does this proof and the advantage is still ...
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Can Paillier ,RSA or any other schemes be used for universal re-encryption like elGamal?

ElGamal, RSA, and Paillier cryptosystem have homomorphic property, and can be used fro re-encryption purposes. I want to use the encryption to re-encrypt ciphertext(as in proxy re-encryption but ...
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Finding d when given p q and e [duplicate]

Say I have these values: p = 5 q = 11 n = 55 phi = 40 e = 7 I need to code this in python to get d for the decryption part. I understand how to write this down and work it out on ...
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RSA-FDH Signature Scheme EUF-CMA

I am aware of attacks whereby an attacker is able to forge a message IF the hash of the original message is the same hash as their current message. The question is, is it still possible for RSA-FDH to ...
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How re-encryption can be done through RSA

Both RSA and Elgamal have homomorphic properties. So both can re-encrypt the ciphertext. Re-encryption with Elgamal works as seen here. How does re-encryption work using RSA? What modification / ...
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Can I remove newlines in a public key?

Can I remove new lines from the RSA public key file to get a one line string? So the question is if the key looks like this AAA BBB CCC or ...
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1-out-of-2 Oblivious Transfer Security

Just started reading Oblivious Transfer. I am searching for a proof of security based on RSA implementation but I can't find anything simple to understand. Can someone direct/show me to an easy to ...
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Decrypting arbitrary numbers with RSA

I want to construct a hash-chain where I want to share millions of small AES-128 keys with Bob over a period of time. Bob should not be able to predict the future keys if he knows the past keys. I ...
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Why does square root $\pmod n$ find $p$ and $q$ (as $n = p \cdot q$)?

Let $n = p*q$, with $p \neq q$ and $x^2=1 \pmod n$, $x+1 \neq 0 \pmod n, x-1 \neq 0 \pmod n$ (So x is a non-trivial square root mod n.) I don't see how $\gcd(x+1,n) \in \{p,q\}$ follows. I ...
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Does choosing N to be product of safe primes avoid William's p+1 factoring attack on RSA?

In this post, I found that choosing RSA modulus $N$ to be product of safe primes avoids Willam's $p + 1$ factoring attack. Suppose $N = p \cdot q$, where $p$, $q$, $(p-1)/2$ and $(q-1)/2$ are primes. ...
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RSA and One-time Password (OTP) service

What is the expert cryptographic opinion on the following? Assume that there is a web server and a Client on web page who calls an OTP ([One-Time Password]) web service on the server which: creates ...
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Attack on security model for RSA-FDH

I recently read in Cryptography textbooks and online videos that compared to Textbook RSA which is insecure against Chosen Plaintext Attacks (CPA) and Chosen Ciphertext Attacks (CCA), RSA-FDH is ...
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Is this toy RSA demonstration flawed?

I want to present the basics of how RSA works to an audience of beginners in cryptography. The problem is that I am lightyears from being an expert. After reading about how RSA works in wikipedia, ...
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Can the RSA accumulator scheme be converted to Elliptic Curve math?

Is it possible to translate the RSA accumulator scheme directly to EC without requiring bilinear pairings? In RSA we have: $A_{n+1} = A_n^c$ st. $\{c \: \textrm{prime} \: | \: c \in [\...
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Anonymous trust/reputation system

Suppose there are 3 persons, Alice, Bob and Peter. They are identified by their pseudonyms (public RSA keys). Alice has a key Alice, Bob has ...
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Establish Trust By Signing Random Seed

I'm trying to get my server to establish trust with a client. Neither is on the Internet, so there are no certificate authorities. The typical way to establish trust in my domain is for a client to "...
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How to decide whether to use digital signature (RSA) or HMAC

I found multiple posts regarding the differences between HMAC and RSA. Why should I prefer one or the other? These are some examples: HMAC SHA256 vs RSA SHA256 - which one to use What are the ...
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Validating JWT works with small changes to public key, why?

I was trying to verify the following JWT on JWT.io with the following public key: ...
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Signing a binary hash vs character representation of the same hash

I have a hash that I want to sign, with the hexadecimal representation: hash_bin=0x11223344 (length 4 bytes). The same hash also has a character representation hash_text=”11223344”, which is the ...
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Understanding need for PKI

For simplicity let's say I only have RSA and AES on my hands and I want Alice to talk with Bob over a secure channel. With secure I am implying no MITM and Alice and Bob know they are talking to each ...
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Security of RSA public key depending on how it's computed [duplicate]

I understand that the public key in RSA encryption may be computed using Euler's totient function or Carmichael's totient function. I'm now trying to figure out how the choice of totient function ...
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Is there an intuitive explanation as to why only the private key can decrypt a message encrypted with the public key?

I have just learned about using PGP/GPG for email encryption and one thing bugs me: How is it possible that a message encrypted with somebody's public key can be decrypted only with that person's ...
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Recommended key size for DKIM

What is the recommended key length for DKIM? I'm currently thinking about a 1024-bit key vs. a 2048-bit one. From the crypto point of view for RSA, 2048 or 4096 bits is clearly recommended--no ...
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Why RSA2048 sign of Intel accelerate card is fast?

Intel accelerate card This card executes rsa2048 sign 35K ops(operation/second). My fast version is only 100 ops. I can't find any HSM paper that has same performance level. I am interested in this ...
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Make AES CBC more secure by destroying each block? [duplicate]

Assume AES in CBC mode is used to encrypt an arbitrary file. The key and the IV are generated out of secure random data and are both different for each file and of proper length and strength. Then the ...
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Is there any rules for choosing the two primes that's used in generating RSA keys? [duplicate]

So I want to ask is there any rules for choosing the two primes that's used to generaten in RSA? I mean clearly you can't choose 2 and another super big number, so ...
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Precise Definition of 1-out-of-2 Oblivious Transfer

What's the precise definition for 1-out-of-2 OT? and what's the best way to show that it can't be achieved under unconditionally secure setting? I am reading about it and just couldn't get my head ...
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Differences between Gcd and factoring

please can someone explain to me the difference between the following. Using two different numbers I. E one is the rsa key and the other a number working from 2 upwards to work out the Gcd, until the ...
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Does larger key size mean larger data size in asymmetric encryption?

I'm new to cryptography. I know the larger the key size (like 128-bit vs 1024-bit) the harder the ciphertext is to crack, generally. But assuming everything else being equal, does a larger key size ...
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How to calculate M when the attacker know e and w [closed]

Alice has a pair of RSA keys, the public key is $(n,e)$, the clear text message $M$ and the ciphertext $C=M^e \pmod n$. We suppose that Bob wants to encrypt two successive messages and send them to ...