# 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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### Algorithm for factoring a 30 decimal digit number

My professor has given me an RSA factoring problem as an assignment. The given modulus is 30 decimal digits long. I have been searching a lot about factoring algorithms. But it has been quite a ...
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### Is there a maximum number of encryptions I should make with the same RSA key?

From an answer to the question RSA maximum bytes to encrypt, comparison to AES in terms of security? I learned that there is a theoretical limit of how much data can be safely encrypted with symmetric ...
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### Compared with plain RSA , what is the advantage of randomised public key encryption scheme such as EIGamal encryption?

I am new to cryptography, I am very interested in cryptography, thank you for your answer.
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### Finding Private key in RSA with public key, cipher text and plain text

Is there a known 'non-brute force' method of determining a private key in an RSA system when all other parameters are know? I found the values of a ciphertext ($C$), its corresponding plaintext ($P$) ...
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### On what basis is padding chosen in OpenSSL?

I am using CAPI Engine in OpenSSL and I did some test. When I use TLS 1.0 or 1.1, during handshake and RSA signing, PKCS padding is chosen. When I use TLS 1.2, RSA signing uses PSS padding. What ...
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### Unable to determine plaintext from ciphertext

Given the letter-number cipher: a=00, b=01, c=02, etc., encrypt the word 'hi' and decrypt its ciphertext using RSA. The public key is (5,35) and the private key is (29,35). I know that 'hi' is ...
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### get q from p in rsa [closed]

i want to get q, but i dont know how. Informations: N = ...
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### RSA: Construct private / public key for given cipher and plain text message

let's say we are given a classical RSA encryption scheme, though we would like to "reverse" the task: Given two messages $c, m$ choose $p, q, e$ such that $p, q$ are prime and $c ^ d \equiv m\pmod N$ ...
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### Message input format for RSA algorithm

I was trying to implement the RSA algorithm myself. I have written the key generation part. My question is if I have the word "apple" which I want to encrypt, do I have to convert each alphabet to ...
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### Implementing ESignature and digital certificate

I'm having some issue understanding the mechanism of electronic signature and how implementing it Here what I understood, correct me if I'm wrong: (Client is here an android or ios device. Server ...
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### I don't understand RSA encryption (specific questions)?

So I've been studying RSA for a class and I'm having a hard time understanding how it works. Why do we choose the value of e such that e is relatively prime to the totient (as opposed to just being ...
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### With node-jose, Should I expect the JWK -> PEM conversion to be reversible?

I am using node-jose to convert a particular JWK to a PEM, and then ... converting that PEM to a JWK. The resulting JWK has the same e, but different n than the original. Should I be surprised? I ...
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### Protocol for proof of knowledge of $l$-th root

Assume we have Group G in which the adaptive root assumption holds. This assumption states that if we choose an element $w$ and after that, if we receive a prime value $l$ it is hard to find the $u$ ...
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### Is RSA encryption with a private key the same as signature generation?

It is often said that RSA encryption of a cryptographic hash with a private key is the same as signing (signature generation). And that verification consists of decryption using a public key. Is RSA ...
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### How to use separate keys for signing and encryption

I read that the same key should not be used for both certificate signing and encryption. I wonder if this is not a problem with PKI/TLS/SSL, the reason being asymmetric encryption is used to transmit ...
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### RSA with a prime substituted by a Carmichael number

If the public key in a RSA system is $(n,e)$ with $n=pq$, $p$ prime, $q <p$ a Carmichael number and $\gcd(e,(p-1)(q-1))=1$ then if $d$ is the inverse of $e$ modulo $k=(p-1)(q-1)$, I want to show ...
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### Feasible to find two sets with the same RSA accumulator value if a prime representative hash function is used?

Consider the RSA accumulator scheme with random oracle as proposed by Barić and Pfitzmann, with the random oracle replaced by a secure hash function $H$ as follows. For a set $S$, the accumulator ...
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### Private exponent on RSA key

this is the first time I write here. I'm studying a library to encrypt/decrypt with RSA algorithm. In an example given by the library I found this: ...
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### (Cracking RSA) How to calculate the Private Key using Public key, p,q,r,n? [closed]

I have been given the following values : ...
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### Accidently deleted “~/.gnupg/pubring.kbx” , how to recover keys [migrated]

is there is any way to recover the encryption keys in this case, since they really important 1) the issue: i've lost my gpg key identifiers by deleting ...
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### Can there be more than one valid private exponent for a given p, q, and e in RSA encryption?

For example, given: p = 173, q = 149, e = 3 Using phi(n) gives d = 16971 While using lambda(n) gives d = 4243 Both values satisfy the checking equation (de)%phi=1, so are both correct, and if so, ...
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### Encrypt and decrypt data accessible by two users on the web on multiple devices

I am currently building a website where a user will be able to upload a file to my server and another user will be able to download the file. Now i want to add encryption to this with the following ...
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### Anatomy of an RSA private key

I'm learning about OpenSSL and public key infrastructure and am curious about the structure of an RSA key and how it's related to its corresponding public key. I can generate a private RSA key with ...
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### Relation between signature size and message-digest length in RSA PKCS#1v1.5 sign/verify

When using RSA-PKCS#1v1.5 to sign and verify a message-digest, is there a compulsory relation between the sizes of message-digest and the key/signature ? For example, If I use key/signature length of ...
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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 ...
702 views

### 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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### Exclusion proof cost

I am trying to understand what is the cost of non-membership verification for a universal accumulator? More specifically, how can I compute it? Whether using an accumulator is more efficient than ...
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### Factoring $n$ in RSA knowing $e$ and $d$

I know that if $(n,e)$ is the public key in RSA and we also know $d$ the private key, then there is a probabilistic algorithm to factor $n$. I'm reading the proof from Fact 1 on here. I understand ...
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### How to derive a 4096 bit or 8192 bit RSA private key from a (BIP39) mnemonic seed?

How to derive a 4096 bit or 8192 bit RSA private key from a (BIP39) mnemonic seed? Any tool available for this?
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### What is blindness and forgeability in chaum blind signature scheme?

I am going through the voting protocols. I know how blind signature works (Blind Signature), but why is blind signature - unconditionally ”blind”, conditionally ”unforgeable" (as highlighted in the ...
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### Constructing an integer with specific totient without factorization

Given $N(=pq)$, but not its factorization. Somehow you manage to know, that $k$ divides $\phi(N)$. Is it possible to come up with an integer $N^{*}$, for which $\phi(N^{*})=\phi(N)/k$, without ...
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### Common modulus attack with not coprime exponents

lets suppose we have the public keys $(n,e_1)$ and $(n,e_2)$, such that $\gcd(e_1,e_2)=d>1$, and the same message encrypted with these two keys. I'm trying to see if common modulus attack on RSA ...
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### JWE between Android/iPhone and backend

I'm working on a solution where JWE is needed between an Android app and a backend written in Node.JS, using node-jose. I've been struggling a lot since it seems ...
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### Prime Factorization in RSA always leads to the product of two primes?

Lets prime factorize $30$: $$30 = 3 \cdot 10 = 3 \cdot 2 \cdot 5$$ We see that the number $30$ is a product of $3$ primes. But in RSA, when factorizing huge numbers, we always seem to only get two ...
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