# 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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### Can the hash of a PKCS1 v1.5 RSA signature be used as a key derivation function?

I know this sounds crazy, but hear me out. As a follow-up to Can the AES-GCM authentication tag be used as a key derivation function?, I'm also considering more creative solutions to derive unique (...
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### How to hack pass-protected private RSA key

I know nothing about cryptography. I must present a completed ASP project to my university that proves I have learned clingo. I have heard that the task of recovering the plaintext private RSA key ...
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### Zero knowledge RSA public key

Suppose Bob has $k>1$ RSA public keys $(e_i, n_i)$ without any knowledge of their corresponding private keys. Alice also has all the public keys, but also has a private key for only one of them, ...
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### Cracking RSA (or other algorithms) manually by a savant

RSA cryptography strength comes from the hardness (or so we believe) of factoring big numbers. For key lengths over 2048 bits, it is infeasible for current or near-future computers to factor those ...
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### Completing RSA Encryption

Being new to cryptology, I'm trying to understand how I would complete RSA encryption by hand. I can only follow the formula so far before becoming very confused. I want to encrypt the value "123&...
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### How is it possible to derive the public exponent from an RSA private key?

I am gonna write down formulas that I know and use to generate RSA keys. we choose $p$, $q$ $N = p\cdot q$ $\varphi(n) = (p-1)\cdot(q-1)$ choose $e$ such as $1 < e < \varphi(N)$ $e$ is coprime ...
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### CrypTool RSA Features [duplicate]

I am attempting to manually encrypt a plaintext message (message = MI) using RSA. I receive an answer of: 33,264 and 21,164. When I enter the same plaintext into CrypTool to confirm that my ...
137 views

### Am I Doing RSA Correctly?

I am trying to figure out how to complete RSA manually. I am trying to encode a simple block message (Mi). I used CrypTool to determine the encryption. When I "manually" computed the ...
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### Decrypt Ciphertext Using different private key, given knowledge of original private key [duplicate]

A message, m is encrypted using a private key d. ...
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### Verifiable Delay Function - Fake Proofs

For unknown group order such as RSA groups $G %$, it takes $T$ sequential steps to compute the below function (time-lock puzzle). $$y = g^{2^T} mod N$$ This paper states that if $/Phi(N)$ (Group ...
359 views

### Is it alright to generate RSA keys with bit sizes other than 512/1024/2048?

I am keep generating RSA keys for 512/1024/2048/4096... as bit size. Each time the key length is increasing. Is it possible to generate/use keys other than the ...
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### Decrypt encryptedKey session key using - AES-128 - PKCS-1#rsaes-kem-kdf2-kw-aes128

I have basic knowledge about how encryption algorithms work such as RSA, AES and so on. I have an XML response encrypted with both AES and RSA. I tried using OpenSSL to decrypt with several steps but ...
261 views

### VDF / RSA groups

I believe I am overthinking it; however, I need to clear out my doubts. What is exactly RSA groups and how their order is unknown? I know in RSA N is computed by multiplying two prime numbers (p and ...
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### RSA encryption key conditions

I recently read the RSA cryptosystem but now I confused in key generation phase. According to the Euler's Theorem, we have just one condition: e.d = k.ϕ(N) + 1 where: "e" is encryption ...
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I'm working on a CTF. The challenge is to get the contents of an encrypted message given the ciphertext and the 2048-bit RSA public key. I did finally get the flag after a few hours, but I'm still not ...
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### Given $e$ and $d$, find $\phi(n)$

Let's say we have just RSA public and private exponents $e$ and $d$ but not the corresponding modulus $n$. Is there a method to find $\phi(n)$? This is for a CTF challenge. I am not concerned about ...
236 views

### Security of RSA-3072 with public exponent $2^{16}+1$

NSA recommendation for the pre-quantum period allows the use of RSA-3072 (https://apps.nsa.gov/iaarchive/programs/iad-initiatives/cnsa-suite.cfm), nevertheless, is it safe enough to do it with the ...
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### RSA vs diffie-hellman + polyalphabetic cipher

My basic question is: How does RSA compare to using Diffie-Hellman + <some symmetric key crypto, e.g. a polyalphabetic cipher> Let's assume that factoring large numbers and computing discrete ...
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### What is the 2021 Padding Recommendation for RSA?

What is the current, year 2021, padding Recommendation for RSA? PCKS1? 7? 11? OAEP?
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### Large e in RSA but not Wiener attacks

How to find $d$ with large $e$ ? If $(3\cdot d)^4 \le n$ : Wiener attacks, so what if $(3\cdot d)^4 > n$ ?
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### How is hybrid (RSA+DH) more secure than RSA quantitatively?

Is there any graph that serves as a comparative analysis for the factorization problem vs discrete logarithn problem? I am implementing an hybrid encryption algorithm (RSA + Diffie-Hellman) and it is ...
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### Is there much difference in a RSA-4096 over RSA-3072 for support/speed and security?

I am in the process of created a signing certificate and i have an option of RSA-4096 or RSA-3072. Is there much difference in security between the two? I know people say RSA-3072 should be good until ...
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### Given N and e in RSA and the ability to get signature s for any message m, can you find the value of the private key d?

Given N and e in RSA and the ability to get signature s for any message m ($s=m^d \mod{n}$), can you find the value of the private key d?
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### RSA and Wiener's attack [closed]

I'm trying to do Wieners' attack for the case \ ...
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### Subtle Crypto Algorithm Choice

I need to encrypt some text in the browser to be stored server side. After a little research I decided to use the SubtleCrypto API. I created the the crypto key using the following code: ...
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### detect the RSA public key from encrypted text

we have a service who has a list of public keys got from clients (for example 1000 public keys. not too many) service gets an encrypted message from one of clients. this message is encryped with a ...
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### How can I enhance the security level of my RSA code?

I am trying to enhance the security level of my RSA code that I implemented in Python. I tried to add blind operation, randomized algorithm to my RSA code (separately, not together), but I am not sure ...
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### How many encryptions are needed before OpenPGP key privacy is violated?

According to an excellent answer describing the pitfalls of key privacy in OpenPGP: Theoretically, an all-zero key ID can be used as a way to discourage traffic analysis, but this is not a complete ...
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### Is this protocol secure?

Before anyone freaks out, this is purely speculative and I am not developing a cryptosystem! I can't see anything wrong with this protocol, but my knowledge of cryptography is rather superficial: ...
4k views

### Is it proven that breaking RSA is equivalent to factoring as of 2021?

I can't find any publication that proves this.
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### RSA plaintext repetition attack, (same plaintext, different ciphertext) [duplicate]

Billy wants to send a message to Bob. He generates secure primes p and q for each time he sends a message. However, he ...
1k views

### Does the security of RSA come from just the carries in multiplication?

Although it's hard for me to find a reference, it's my understanding that if you calculate $N = pq$ using $GF(2)$ polynomial multiplication rather than ordinary multiplication, it is easy to factor $N$...
Lehman's method can be described as; Let $N=pq$. If the ration of $p/q$ is near a ratio of two small numbers $r/s$, then $ps$ and $qr$ are close to $\sqrt{nrs}$. The Fermat's method can be easy ...