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.

Filter by
Sorted by
Tagged with
0
votes
0answers
27 views

Decrypting RSA with no private key [duplicate]

Let's say I'm given an RSA-encrypted message and RSA public key pair ($e$, $N$) such that $N$ is prime.$e$ and $\varphi(N)$ are not coprime, hence I can't find the private key $d$ via modular inverse. ...
2
votes
1answer
104 views

Would asymmetric cryptography be feasible in World War II?

Assuming people in the forties would have known asymmetric cryptographic methods like RSA, would they have been able to make sensible use of them? There were no real electronic computers at the time, ...
2
votes
0answers
91 views

Can I use RSA as hash function?

My end goal is to have an encryption function $e$ and a hash function $H$ such that for all m we have: $$H(e(m)) = e(H(m))$$ This would work if we use RSA encryption along with RSA "hash", ...
0
votes
1answer
45 views

Choosing UWP encryption algorithms

I've just come across the large variety of encryption ciphers available in the UWP WinRT API, both symmetric and asymmetric. I'm trying to figure out which are commonly seen as the most favourable ...
0
votes
0answers
5 views

Convert a test message to an integer for ciphertext in RSA [migrated]

The function ConvertToInt(message) should convert a text message to an integer and Encrypt(message,modulo,exponent) to return the integer ciphertext. Now, I take a message and convert the ASCII value ...
7
votes
0answers
152 views

In RSA, given public key $(n,e)$ and $d^e\bmod n$, can we factor $n$?

Given an RSA public key $(n,e)$ and the textbook-RSA encryption $c$ of a valid matching private exponent $d$, computed as $c\gets d^e\bmod n$:  can we factor $n$ ? Assume $n,e,d$ are per PKCS#1v2.2. ...
1
vote
2answers
134 views

With RSA or ECC, if I encrypt my private key with my public key, is there a way to recover my private key?

Is there an algorithmic, mathematical, technical or implementation "hack" to recover the private key or is it definitively encrypted without any particular mathematical property, like any ...
0
votes
1answer
81 views

How to compute $m$ value from RSA if $phi(n)$ is not relative prime with the $e$?

Here is some information we got : We know the value of $n$, with size $1043$. We know the value of $p$ (size $20$) and $q$ (size $1023$) as the factors. $e = 65537.$ $\varphi(n)$ = $(q-1)(p-1)$ When I ...
-1
votes
1answer
56 views

How to recover RSA messages if they are padded with spaces?

I have a message m="hunter". Let's say we pad it with 2 spaces from the left making the final message as ...
0
votes
0answers
27 views

RSA PADDING WITH e=3 [duplicate]

I have a ciphertext which has been padded with spaces from left the message is 31 bytes long and e = 3 how can I recover the message with python code .
4
votes
1answer
87 views

Consequence of $p\bmod e=2$ in RSA prime generation

When generating a prime $p$ for use in an RSA modulus with public exponent $e$, it is necessary that $\gcd(p-1,e)=1$. When $e=3$, and since $p$ is a large prime, that implies $p\bmod e=2$. Assume an ...
2
votes
2answers
417 views

RSA: How close d should be to n, given default public exponent e = 65537

For small public exponent e, private exponent d should be less than but close to modulus n. Is there any particular test, applied in common implementations, to verify that? If so, what would be the ...
0
votes
1answer
43 views

How to Update Non-Membership Witness upon deletion in RSA Dynamic Universal Accumulator

The Universal Accumulator paper mentions the following for updating non-membership witness upon member deletion. Choose $r$ such that $a\hat x − rx ∈ Z$$2^l$ What is Z$2^l$ and how can we ...
6
votes
2answers
321 views

Definition of $x^u \bmod k$

In RSA, $C=M^e \bmod N$ and $d=e^{-1} \bmod φ(N)$ are used for encryption and signatures. What is the exact definition of $x^u \bmod k$? Also, what is the difference between $$x^u = y \bmod k$$ and $$...
1
vote
1answer
409 views

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 ...
0
votes
0answers
31 views

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 ...
3
votes
0answers
15 views

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 ...
0
votes
1answer
38 views

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 ...
-1
votes
1answer
53 views

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 ...
2
votes
1answer
133 views

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 $n=143$,...
1
vote
0answers
44 views

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 ...
0
votes
1answer
25 views

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 $s$ (...
3
votes
0answers
65 views

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 (...
0
votes
0answers
35 views

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 ...
1
vote
0answers
48 views

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 ...
1
vote
0answers
23 views

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 ...
3
votes
1answer
146 views

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?
0
votes
1answer
31 views

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))?
1
vote
1answer
48 views

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.
0
votes
1answer
39 views

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 ...
0
votes
0answers
35 views

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')^{\...
7
votes
2answers
421 views

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 $n$?
0
votes
0answers
86 views

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 ...
0
votes
0answers
44 views

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.
2
votes
1answer
105 views

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 ...
3
votes
2answers
78 views

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 ...
0
votes
0answers
22 views

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 ...
0
votes
0answers
19 views

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 ...
2
votes
1answer
101 views

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 $\phi$...
1
vote
1answer
78 views

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 $...
2
votes
2answers
265 views

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 ...
0
votes
1answer
47 views

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 ...
0
votes
1answer
92 views

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 ?
0
votes
1answer
64 views

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 ...
0
votes
1answer
73 views

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 ...
3
votes
1answer
54 views

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 ...
1
vote
1answer
75 views

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 ...
0
votes
1answer
71 views

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?
0
votes
0answers
29 views

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 \...
0
votes
0answers
47 views

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.

1
2 3 4 5
43