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 with proper paddings.

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RSA code giving result after more than 10 minutes

I am trying to implement RSA algorithm. I got a code in python. When I run it, it takes more than 10 minutes even when the primes are within 100 and message size is 8 decimal digits. Plese suggest ...
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How would I get started in auditing and finding vulnerabilities in encryption algorithms?

I know, it sounds dumb. Very dumb in fact. But regardless, I want to actually begin doing security research on cryptographic algorithms (SHA, RSA, ECDSA, etc.). I would prefer that this question be ...
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Man in the middle on public encryption by sending vecitem your public key and save the real one

I was reading on public encryption and I read that if you connect from somebody else network he cant figure the massage you send. but what if he commit simple man in middle just that instead passing ...
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Security of receiving RSA-PSS computed mask in verification step

I'm trying to verify an RSA-PSS padding in an ethereum smart contract The code to compute the MGF step (i.e. calculating many SHA1 hashes) is very expensive in terms of computaiton costs (gas) on ...
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How to devise cryptographic system with data-sharing ability and password reset

I originally posted this in the security.stackexchange forums but then I was directed to this one which seems more befitting for my question. I am writing a C# .NET application. For my application the ...
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How to declare 2048 bit key in RSA

I want to implement RSA algorithm using C language. I have read the size of primes in RSA like p and q are 2048 bits long. How to declare such 2048 bit values in C. As i know that the data types like ...
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How to recover a message with shared modulus for textbook RSA

Same message sent to two users encrypted with textbook RSA, known $n$, $e_1$, $e_2$, $c_1$, $c_2$. Show how the attacker can recover the message. Problem statement Consider an RSA system with $n=143$,...
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Content Key Encryption for Multi-User data access

I recently worked out a concept for a use-case, but I'm not sure if my approach is good enough. So I would appreciate feedback and things to look out for, as I'm fairly new to this field. A User can ...
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Why blinding integer $r$ needs to be co-prime with $N$ in blind RSA signature

According to blind RSA signature wiki the random value $r$ in $m^\prime=mr^e \bmod N$ needs to be relatively prime to $N$. Why is this a requirement? A follow up a related question: after $s$ (...
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How to convert a 4 digit number (supposedly the PGP private key) into a PEM format and how to code this? [closed]

Someone sent me a PGP encrypted message (it's not a file but in a text message) and the private key to decrypt it is not given. But he gave me a hint, that the private key is a 4 digit number. I can ...
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Key strength comparison: symmetric key vs RSA/DH key

I came across different reputable sources quoting different equivalent symmetric key strengths for RSA/DH keys. This NIST paper (page 67) states the following offer corresponding security strenghts (...
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RSA encryption/decryption values not working as expected [duplicate]

I'm faced with an issue I can't seem to understand when it comes to RSA. Below are my values for all of the parameters, unfortunately I can't seem to get the expected decrypted values from my ...
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Retrieve message from rsa ciphertext based on some conditions

Let's say: $x = m^{e-1}\bmod n$ $y = m^{d-1}\bmod n$ Here $m$ is a message, $e$ is public exponent, $d$ is private key and $n$ is the modulus. Now if I know $e, x, y$, and $n$, can I retrieve the ...
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Generating a recovery phrase for a RSA key-pair

What is an optimal way to associate a RSA key-pair with a recovery phrase/seed for access recovery purposes? I've seen a lot of cryptocurrency wallets provide this feature, however, I'm not looking to ...
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Is choosing $1$ as a public exponent valid in RSA?

I know it will not encrypt anything. But is $1$ valid as a public exponent in an RSA public key?
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How to solve high exponent attack for same message in RSA

I know Håstad's broadcast attack when e = 3, but what if e = getPrime(randint(350))?
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Is possible that find numbers where the product of 3 numbers is congruent modulo to 1?

It is possible that find the $a, b, c$ randomly in here? $$ abc \equiv 1{\pmod {\varphi (N)}} $$ Instead of $$ de \equiv 1{\pmod {\varphi (N)}} $$ in the RSA Algorithm.
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How to find m so that RSA cipher end with '\x00'+SpesificString , if we freely input the plaintext?

I have an RSA encryption with public key $(3,n)$ with 2048 bits modulus $n$. I want to find the value of the plaintext $m$ so that the ciphertext (in bytes representation) value ends with ...
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How does CL signature work?

I'm studying the CL signature that how can it works. However, I cannot understand how equation (42) is calculated. What is the last three factors? The value T is as follows: $$T \leftarrow(A')^{\...
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Calculating RSA Public Modulus from Private Exponent and Public Exponent

If I know the private and public exponents ($d$ and $e$) of an RSA key pair, is it possible to (efficiently) calculate the public modulus $n$?
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Can we defends against RSA Timing attack when we use java.math.BigInteger.modPow?

I think that Montgomery and sliding window techniques are applied within java.math.BigInteger.modPow (and more specifically ...
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RSA How many value for d

How many value can have a private key with this format? p,q,d = (19, 41, d) where 1< d <18x40? I want know how to calculate that.
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Montgomery Multiplication with CRT

I am attempting to understand how to use Montgomery multiplication in an RSA private key operation: $X \equiv a^{e} \pmod{n}$ where $a$ is the message, $e$ is the exponent, $n$ is the modulus. Using ...
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How to generate Multiple Encryption Keys for use in RSA polymorphic multiplication

I am a long time scroller, first time poster in the crypto stack. I've recently been finding myself leaving the realm of mainstream/standard crypto (imo that consists of symmetric/asymmetric ...
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Could someone please explain the implementation of public-private key encryption for storing passwords?

As someone new to cryptography,I have a question about how logins work on websites. I understand mathematically how asymmetric encryption works and how https web requests work to securely send ...
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Generate version 3 x509 certificate from version 1 CA

Please do forgive me for my naivety. I have inherited a legacy system wherein the CA which signs the certificate is of version 1. Is it possible to generate a x509 version 3 certificate which is ...
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Is it necessary to use Fermat's Little Theorem to prove the 'correctness' of the RSA Encryption method?

Given a 'message' $M$, a proof of the 'correctness' of RSA encryption means to show that $(M^e)^d \equiv M \pmod{n}$, where $n=pq$ is a product of primes, and $ed \equiv 1 \pmod{\phi(n)}$, where $\phi$...
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RSA: Is there a way to digitally sign a message without knowing the private key?

So, I am following an online course about cryptography these days, and I am stuck in an assignment. Here it is: ---------Known-------------- $m_1$: message 1 $m_1$ = 387 $s_1$: digital signature for $...
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Is it reasonable to consider that an encryption scheme must be invertible?

I am in a dispute regarding a test question in an exam. The question is something like that: What would happen if one were to use RSA with $n=100$ and $e=13$ to encrypt a message $m$? a) You would be ...
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Practical Threshold Signatures

In Practical Threshold Signature it says that there is a requirement in which the RSA public exponent $e$ must be more than $l$. $l$ in this case is the number of players in the threshold group. My ...
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If $((p-1)*(q-1) -1)$ divisible by $e$ ($e$ is odd number) , then $\text{gcd}(e,(p-1)*(q-1)) = 1$

If $((p-1)(q-1) -1)$ divisible by $e$ ($e$ is odd number) , then $\text{gcd}(e,(p-1)(q-1)) = 1$. ($p,q$ are prime numbers ) Is this true, if yes why, if not why not ?
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RSA Encryption that only my family could decrypt

I was doing some thinking about what would happen to my computer and passwords if I fell off the earth tomorrow. I wanted to have a message that only they would have the ability to decrypt and I ...
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Reducing a 64 digit integer to 10 digit

Situation:- I am using Python. I am using RSA and I am using two 64 bit keys. I am not an cryptographer . I can provide you the RSA code if needed but i am not posting it as it doesn't have to do ...
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What is the exact meaning of the public key cryptosystem properties in New Directions In Cryptography by Diffie and Hellman

I'm quite new to cryptography and don't have much mathematical knowledge. I'm studying cryptography, especially public key algorithms. I have some basic knowledge of public key algorithms so I know ...
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Why $f(x)=x^e$ is a bijection i.f.f $e\in{\mathbf{Z^*_{\phi(N)}}}$?

I understand that if $e\in{\mathbf{Z^*_{\phi(N)}}}$ then $\gcd(e,\phi(N))=1$ and if $e\not\in{\mathbf{Z^*_{\phi(N)}}}$ than $\gcd(e,\phi(N))\neq{}1$. But I couldn't figure out why this implies ...
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Format for data & key exchange/storeage [migrated]

Is there a standard format for storing/exchanging encrypted data along with the key needed to decrypt it (data is encrypted with a single use symmetric key and the symmetric key itself is encrypted ...
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KDF for generating RSA and ECC keys from a 2048 bit secret

Do KDFs exist for generating RSA and ECC keys from a 2048-bit random secret?
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Finding the relationship given by the generating elements of a non-abelian group (for a maximum case) where they correspond to finding cycles

Let $G=(\mathbb{Z}_p \times \mathbb{Z}_p) \rtimes_{\phi} \mathbb{Z}_q$, where $p$ and $q$ are odd distinct primes. Let $G$ be generated by the elements $s=(g_1,e_q)$ and $t=(e_p,g_3)$, $g_1,e_p \in \...
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How to get fixed m from different pairs of n, e and c in RSA?

In RSA cryptosystem, if I have two (or more) pairs of public key and also the corresponding ciphertexts, can I get the fixed message from them? I cannot think up any good idea for now.
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Hard-core bits from RSA assumption

I am trying to understand better the hard-core bit property from the RSA assumption. The paper by Håstad and Nåslund shows that every single bit is hard-core. By the result itself, two or more bits ...
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Converting RSA.pub keys to word list

RSA keys are notoriously blobs. I'm looking to make something more human readable. I want to take the mathematical operation and convert it to a number that can be easily expressed as a series of ...
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When is a cryptosystem or its algorithm (like RSA) considered efficient?

When is a cryptosystem (like RSA) or its algorithm for keygeneration, encryption and decryption of messages considered efficient? Is there some bound in complexity which splits both efficient and not ...
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Multi-users RSA problem

Rivest and Kalisky's RSA problem considers various notions on security of the RSA One-Way Trapdoor Permutation. They do it only from the perspective of a single user. What's the state of the art in ...
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Fixed point in RSA encryption

Some papers count the number of the fixed points in the RSA encryption algorithm. They're a minimum of 9 and the real number depends on the smoothness of primes $p$ and $q$. It very unlikely that a ...
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Computational trapdoor where the problem is tractable for both parties but easier for one

Usually the sort of trapdoors which are talked about are designed such as to make the computation intractable for one party and tractable for the other. But what if one party merely has a big ...
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Proving the knowlege of e-th root in an non-interactive way

Just like in this question: Protocol for proof of knowledge of $l$-th root I want to prove that for $u^e = w$ I know $u$ without revealing it. Three other requirements are: e is small (65537) The ...
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Is it safe to reuse the same random session number r in the Guillou-Quisquarter protocol?

I basically use the method below, one difference is that after receiving the first proof the verifier asks the prover to create a proof for another challenge d and this several times without having ...
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RSA assumption and relationship given by generating elemts of a Cayley graph

I have read a very interesting description of computation related to the RSA group as follows. "By the Chinese remainder theorem, we have that: $$(\mathbb{Z}/pq\mathbb{Z})^* \cong (\mathbb{Z}/p\...
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Asymmetric Cryptography decryption

I am new to cryptography, i know essential part of asymmetric cryptography but is it possible to decrypt 617 decimal digits (2,048 bits) with RSA ? How it can be factored?
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Generating RSA keys with plain and ciphertext [duplicate]

I have plaintext and ciphertext. Is it possible to generate an RSA key pair that encrypts the plaintext to ciphertext and decrypts ciphertext to plaintext. I don't need to find the original key pair ...

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