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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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RSA exercise with known $n$ and $e$

Bob decides to use $n = 697 \rightarrow 17 × 41$ and $e = 33$ as his public key for an RSA cryptosystem. Show that the decryption exponent is $97$. Find the encrypted form of the message $17$.
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125 views

RSA encryption/decryption process is not working correctly

I'm trying to apply the RSA cryptosystem to encrypt a byte M=72, using predefined modulus n, public key exponent ...
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2answers
509 views

Is semantic security important in a hybrid cryptosystem?

RSA doesn't provide semantic security when used unmodified, and neither does the commonly used PKCS#1 v.1.5 padding scheme for encryption. Is this a problem for hybrid cryptosystems at all? My ...
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RSA restore part of D from E and N

I have full bits of public key $(n,e=65537)$ but from the private key, I have the lower half bits of $d$. Can I restore the whole RSA private key from that data and use it for decryption?
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717 views

Is RSA provably secure in the sense of Douglas Stinson's ``provable security''?

Here's a quote from Douglas Stinson: “[i]f a cryptosystem can be ‘broken’ in some specific way, then it would be possible to efficiently solve some well-studied problem that is thought to be ...
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40 views

Is it possible to generate same RSA key on purpose?

I want to ask if I have a RSA private key can I use it to generate RSA key that is identical. If yes how can I do it?
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1answer
28 views

Can we find the exact number given remainder of the numbers with mod m?

I have around 1500 numbers. The numbers $x_i$ are calculated as $x_i$=($p*t_i$) mod m. $p$ constant and same for all the numbers while $t_i$ are chosen randomly everytime. For example the given ...
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43 views

Can you tell how many times data has been encrypted?

I'm using multiple RSA keys to encrypt a piece of data. The data length is constant but the data itself is not. Each time I encrypt I prepend a 64 bit string to the newly encrypted ciphertext. This ...
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1answer
55 views

The 9 lives of Bleichenbacher's CAT, it puts another scratch again

Bleichenbacher demonstrated a padding oracle attack against RSA implementations that follow the PKCS #1 v1.5. Through the years, there are various mitigation techniques developed as OAEP and limiting ...
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1answer
43 views

RSA engine with inaccessible private keys - susceptible to any attacks?

We are going to integrate some hardware accelerator for RSA into our next system on chip. This chip can accelerate the core RSA operation, i.e. modular exponentiation $y=A^x \mod(N)$. The private key (...
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63 views

Find factor of a numbers of around 3500 bit long, given 1000 such numbers. Each number is product of s*p, p is constant and s is randomly chosen

Given 1000 numbers of form s*p, number are of 3500 bit long. How to factor these numbers? s and p are not necessarily prime numbers. p is constant for all numbers and s is randomly chosen for all ...
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1answer
42 views

Send content to owner of gpg public key, nested content symmetric encryption

If I want to encrypt a text content file using a symmetric algorithm like AES, is there a standard format gpg will expect, where it can detect a symmetric key (encrypted with recipient gpg public key ...
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1answer
80 views

RSA find $q$ given only $e$ and $p$

Lets say hypothetically all one knew was a value of $e$ and a value of $p$. As an example, lets assume that $e = 13$ and $p = 67$. Would it be possible to find the value of $q$ from this equation? ...
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37 views

RSA limiting down the possible values for $n,q$, and $d$? given only $e$ and $p$ [duplicate]

Suppose someone forgot the value of $n$ and you only knew the values for $e$ and $p$. How could one go about limiting down the possible values for $n,q$, and $d$? I'm thinking to try and solve $\gcd(...
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1answer
116 views

Performing a dictionary attack on RSA/ECB with no padding

I have the exponent $e=2^{16}+1$ and modulus $n$ (154 digit number) of an RSA public key along with the ciphertext (64 bytes) encrypted using the same key with RSA/ECB and no padding. I am required ...
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1answer
36 views

Equivalent RSA modulus for NIST P-192 and P-521 elliptic curves [duplicate]

At www.keylength.com, I found the following table of ECC field size and the corresponding RSA modulus recommended by NIST. ECC Modulus RSA Prime Size 160 1024 224 2048 ...
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1answer
219 views

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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Impacts of not using RSA exponent of 65537

This RFC says the RSA Exponent should be 65537. Why is that number recommended and what are the theoretical and practical impacts & risks of making that number higher or lower? What are the ...
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What exactly is an RSA UFO and what are its cryptographic properties?

I recently read a page describing what is called an "RSA UFO", or "generalized RSA moduli of unknown complete factorization". Though they practically spell out the properties and generation algorithm ...
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3answers
46 views

For elliptic-curve cryptography, does a 256-bit key imply that $x$ and $y$ are each 256-bits or 128-bits?

In the wikipedia article, the claim is made that "256-bit elliptic curve public key should provide comparable security to a 3072-bit RSA public key". Since, in ECC, the public-key consists of a point $...
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34 views

Recover message in RSA-OAEP with fixed seed

In RSA-OAEP given a fixed and a known value for the seed, is it possible to recover message using its ciphertext and the public key $(n,e)$?
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47 views

Unable to reproduce correct signature data

"Skatteetaten" is the Norwegian tax authority. We're currently trying to implement signing of messages for digital cash registry systems and i'm not able to reproduce the desired signed data. Went ...
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RSA with modulus product of many primes

I would like to ask what happens if we build an RSA system with modulus a product of more than 2 primes, for example let $n=p_{1}p_{2}...p_{L}$. I know only the classical RSA system with $n=pq$ with $...
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1answer
69 views

RSA encrypting private keys blinding

I am studying RSA couldn't understand this question: Alice encrypts the private factors of the modulus using her private key. In order to increase security, she multiplies them with a random integer $...
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2answers
423 views

What is the best way to sign a message using RSA?

I was preparing for competitive exam, and I came across this question. I had a lot of discussion with my friends before I resorted to posting it here and I wanted myself to be clear on this. Let $M$ ...
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2answers
20k views

How do I calculate the private key in RSA?

Given $n=pq$ for $p,q$ known, I can calculate $\phi(n)$. $e$ is selected such that $\gcd (e,\phi(n)) = 1$. Using this, how do I calculate the RSA private key? Example: I have $n = 35$, with $(p,...
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RSA: Is there a way to increase the partially encrypt data without knowing the private key?

EDITED QUESTION FOR A BETTER EXPLAINATION I have this crypted information (RSA): ...
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0answers
49 views

Sharing RSA private key between SSH and SSL services. How bad is it?

An appliance uses a curious way of obtaining ssh-rsa host keys: There is a single configuration option "management certificate" that sets RSA private keys both for HTTPS and SSH management. ...
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2answers
791 views

How to forge a textbook RSA signature?

Let $pk=(N,e)$ (resp. $sk=(N,d)$) denote the public (resp. private) key in a plain RSA signature scheme. Define the function $\textbf{Int}: \{0,1\}^* \to \mathbb{Z}_N^*$ as follows: on input string $x=...
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36 views

Is there a variation of Coppersmith's method that applies to disjoint variable set with additional control?

We have a polynomial $f(x_1,x_2,x_3,x_4)\in\mathbb Z[x_1,x_2,x_3,x_4]$ where the only monomials are either from set $$\{x_1,x_1x_2,x_2,x_3,x_3x_4,x_4\}$$ and we seek solutions $(x_1,x_2,x_3,x_4)\in\...
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63 views

Best way to attack a small e and small m RSA problem?

I am working through a series of crypto exercises to learn a bit more about RSA and crypto in general. In the case where one has a small $e$ AND a small m, would it be correct to say that if $m<N^{...
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54 views

Proof of concept for RSA malleability

I'm trying to see how easy RSA malleability is. I generate 2 ciphertexts with a public key: ...
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2answers
82 views

brute force RSA [closed]

I have a ciphertext c_t and a RSA public key pair (e, n). I also know that the encrypted message is a three-letter word in the ...
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1answer
39 views

Why does the Node crypto library do Diffie Hellman this way?

I was sifting through the Node Crytpo library and I came across their Diffie Hellman utility class. Their class implements a generateKeys function that, in their ...
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6k views

Which attacks are possible against raw/textbook RSA?

The PKCS#1 standard defines multiple padding schemes for signature generation/verification (EMSA-PSS and EMSA-PKCS1-v1_5), and encryption/decryption (EME-OAEP and the less safe EME-PKCS1-v1_5). ...
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24k views

Definition of textbook RSA

What is the definition of textbook or "raw" RSA? What are some of the properties of textbook RSA? How does it differ from other schemes based on RSA?
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380 views

My custom handshake

I designed a custom handshake between 2 entities $\rm C$ (client) and $\rm S$ (server) which should meet the following requirements: Requirements: The handshake should make: $\rm S$ know who is $\...
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3answers
627 views

Input limitations on the RC6 cipher

RSA has limitation in input size for encryption and decryption. Can RC6 be used for encrytion and decryption of files larger than 5 MB? Is there any limitation for input size? Is RC6 safe for using ...
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2answers
631 views

Is RSA inspired by Diffie Hellman?

I read a bit of A Method for Obtaining Digital Signatures and Public-Key Cryptosystems that introduced RSA in 1977, and, while learning the steps in RSA a few days ago, I noticed that they are similar ...
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44 views

Size of group for Elliptic curves vs RSA for equal security

For my research, I would like to compare the efficiency of a scheme when instantiated with Elliptic curves and RSA. So, I would like to know a "latest" comparison (as of 2018) on what group sizes of ...
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0answers
40 views

Inclusion and Exclusion proofs in RSA accumulators

I am reading about RSA accumulators from this video and few other sources. I had a confusion whether the complete set is needed to construct a proof of inclusion/exclusion in an RSA accumulator or is ...
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1answer
55 views

Cost of multiplication when e is randomly selected. RSA

Using schoolbook multiplication (which has cost $\mathcal{O}(n^2)$) to multiply two $n$-bit numbers) what is the cost of computing an RSA encryption with $e = 3$? What is the cost if $e$ is chosen ...
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1answer
58 views

RSA How to select a value K such that $e d = 1 + k \varphi(N)$ holds

I am learning RSA cryptography. The part I am stuck on is understanding how k and the public exponent $e$ is selected. Given the formulas; Decrypting: $c^d \bmod N = (m^e)^d \bmod N$ Which is equal ...
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1answer
2k views

crack RSA encryption

According to Wikipedia RSA definitions are : so we have $n$ and $e$ because $p$ and $q$ are prime so there is only one $p$ & $q$ which fit to n so from n we can have $p$ and $q$ so we have $\phi(...
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2answers
68 views

RSA - Does knowledge of part of the ciphertext decrease encryption security for the rest of the ciphertext?

There is a language called SystemVerilog that can be protected via encryption to allow sharing/licensing code for others to use, but prevents them from seeing the code contents. This is done based on ...
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1answer
56 views

How much data can I encrypt with RSA before I need to change the key

How much data can be encrypted with the same RSA key before it has to be changed? I looking for the total amount of data that can be encrypted for a single key pair, not the maximum length of data ...
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1answer
93 views

possibility to encrypt data using AES and RSA frequently? [closed]

I am doing a research for encrypting data, I found many research doing multiple encryption using DES and RSA ? but in symmetric cryptography the best algorithm is AES so I need to do multiple ...
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1answer
92 views

How might one create a system of election by lot (sortition) that is both secure and verifiable?

I've been puzzling recently over sortition, a democratic method of selection for public office which I find very fascinating. Basically, instead of choosing candidates like Hillary Clinton or Donald ...
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1answer
55 views

Which algorithm to use for S/MIME

I'm wondering if the algorithm 1.2.840.113549.1.1.1 (rsaEncryption) is still secure to use for S/MIME encryption. I'm afraid that the scheme is vulnerable against ...
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3answers
268 views

Need a test suite for my RSA implementation

I have an assignment to build a software which can encrypt/decrypt by RSA method. I already did it, but my teacher said that I need to find a test suite (include: modulus, public key, private key) to ...