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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Why has the RSA factoring challenge been withdrawn?

Wikipedia states that RSA challenge has been withdrawn. Does it mean that an efficient factoring algorithm is "just around the corner"? or are there some other reasons? If the challenge was still ...
5
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1answer
90 views

RSA: revealing the modulus factorization by choosing a bad message

I started reading the book Cryptanalysis of RSA and its variants by M. Jason Hinek and I stumbled upon a phrase that intrigued me: plaintext messages that are relatively prime to the modulus (i....
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0answers
94 views

Are Diffie-Hellman, RSA and other types of public key cryptography different? [duplicate]

Are these schemes fundamentally different? Are other schemes fundamentally different in the sense that you can do different operations with them (or the same operations, but needing different ...
6
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2answers
940 views

Do I really need to use the same private/public key pair in RSA?

So I'm making an Android application, I need my application to be only able to scan my own generated QR codes, and I want to make sure that nobody else can generate fake ones. The data isn't ...
6
votes
5answers
5k views

How do ciphers change plaintext into numeric digits for computing?

For example, in RSA, we use this for encryption: $ciphertext = (m^e \mod n)$ and for decryption. If our message is "hello world", then what number do we have to ...
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0answers
277 views

Changing plaintext for encryption in RSA [duplicate]

In the RSA crypto scheme, the message $x$ (plaintext), is encrypted to produce ciphertext ($y$), by computing $x^e \bmod n$. Of course, that means that $x$ has to be a numeric value for this to work, ...
6
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1answer
566 views

Is unusual (non power-of-two) RSA key size more secure?

On this blog https://blog.josefsson.org/2014/06/23/offline-gnupg-master-key-and-subkeys-on-yubikey-neo-smartcard/ there is a following sentence Generate master key Below I will use a 3744 bit ...
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2answers
61 views

Why are asymmetric keys represented as base 64? [on hold]

When one generates a public and private key with say a total of 4096 bits, why does the program output what I assume to be base 64 instead of base 10 or binary?
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1answer
5k views

Can I remove newlines in a public key?

Can I remove new lines from the RSA public key file to get a one line string? So the question is if the key looks like this AAA BBB CCC or ...
7
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1answer
493 views

Timing attack on RSA as used by CryptoLocker?

So far I have researched timing attacks on RSA, We all know the ransomware named CryptoLocker uses RSA 2048 bit encryption. Now, is it possible to break the encryption using a timing attack. I have ...
6
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1answer
126 views

Is solving $m^3 = k*n + c$ hard?

Given the equation $$m^3 = k\cdot n + c$$ I know $n$ and $c$, and I need to find $k$, so that $m$ is a natural number. $n$ and $c$ are large numbers, so i can't use bruteforce. How can you find a ...
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2answers
59 views

Is this RSA signing and verification process secure?

I need to verify that messages in a communications program are from valid senders. Below is a highlevel outline of how I think the process would work. The connections themselves are done over TLS. The ...
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1answer
80 views

Can I calculate $d$ given only RSA’s $c$, $n$ and $e$?

The question “Calculating RSA private exponent when given public exponent and the modulus factors using extended euclid” assumes the factors are known. This got me wondering if it is possible to ...
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1answer
18 views

Extra attributes in a certificate signing request

When creating a certificate signing request, there is a part where openssl says "Please enter the following extra attributes to be sent with your certificate request". One of these is a challenge ...
2
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1answer
22 views

Can MGF1 within OAEP and PSS be replaced by a XOF?

Do we still need MGF1 as used in the PKCS#1 v2.x specifications for SHA-3 hash functions? MGF1 is currently used for OAEP and PSS as Mask Generation Function. Now that the SHA-3 specification contains ...
3
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1answer
384 views

When would I need DSA as opposed to RSA for digital signature?

The digital signature algorithm encrypts a hash using the senders private key and the receiver's public key. This multiple encryption is a pretty expensive process since public key encryption is so ...
5
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1answer
33 views

In PKCS#1 V2.2, should MGF be based on the same hash function that RSA-OAEP-ENCRYPT uses?

In Section 7.1.1 of PKCS#1 v2.2 there are two options for RSAES-OAEP-Encrypt given: Hash MGF Appendix B.2.1 of the same document states that MGF1 is based on a hash function. Is MGF1 based on the ...
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1answer
144 views

justification for method to factorize n knowing RSA private exponent d

I know that knowing the private exponent $d$ corresponding to the private key $k_{pub}\langle n,e\rangle$ it is possible to efficiently factorize n. The procedure starts stating that: $ed -1 = s(p-1)...
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1answer
42 views

Clarification on Key exchange approaches in TLS/SSL

When RSA is used for key exchange in SSL, the client basically encrypts some random data using the server's public key and and sends it to the server. This data is then used to compute the shared key ...
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6answers
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Why MACs are so important despite digital signatures doing everything a MAC can do and more

When an entity A wants to send a message to entity B, he can attach a MAC to the message. Entity B on receiving the message can use the pre-shared key to compute the same MAC and confirm if the ...
0
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1answer
75 views

How to decrypt an RSA ciphertext given an oracle providing the lower 8 bits of decryptions?

I have access to an oracle that can encrypt and partially decrypt a number with RSA-1024 algorithm. For encryption: \begin{equation} C = M^e\bmod n \end{equation} But for decryption, result will ...
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1answer
77 views

Calculating $d$ in RSA?

I've looked in many places including here and can't get quite the answer... So I thought I'd post a question. I can't grasp how $d$ is calculated. Obviously the problem is that knowing $e$ and $n$ ...
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1answer
315 views

RSA and ECDSA Certificate Sizes

Is there a table (or a whitepaper from official sources) that compares the size of X509 certificates generated with RSA (starting from 1024 bits) and ECDSA (starting from 160 bits) ? Thanks for the ...
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1answer
60 views

RSA key generation gives d=1

I was reviewing RSA by hand. I picked 53 and 59 as my primes. For e I picked 5. When I solved for d using extended euclid, I got 1 which obviously doesn't decrypt anything. I checked my answers online ...
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0answers
33 views

What does the encyption part of RSA entail?

As part of an assignment I have to encrypt and decrypt the following two block message (115, 209), using two primes (p = 17, q = 13). e = 5. I computed n to be 221 (17 * 13) and I confirmed that e ...
4
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1answer
43 views

What are the differences between X9.31 RSA operation and PKCS#1 RSA operation?

NIST and other - mainly older - standards often don't just mention PKCS#1 RSA algorithms but also X9.31 RSA algorithms. What are the differences between X9.31 and PKCS#1 (v2.1) with regards to key ...
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2answers
236 views

RSA cipher: ambiguous or break by eth root?

Confused about RSA message cipher: $c = m^e (mod\ n)$ So if $m^e$ can be greater than n, then you can get duplicate ciphers for the same message. Most postings I've read say that $m^e$ must always ...
6
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1answer
85 views

What does Shor's algorithm tell us about the complexity class of RSA and the DLP?

If quantum computers operate in BQP and (using Shor's algorithm) they are able to factor large integers and break the discrete log problem, what does that tell us about the complexity class of these ...
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3answers
111 views

Why is RSA decryption the inverse of encryption?

In RSA, to encrypt a message, the following formula is used: $$c=m^e\bmod n$$ For decryption, $$m = c^d\bmod n$$ is used. However, when I try to substitute the value of $c$ from the first into the ...
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2answers
181 views

How does SSL work on the browser

I recently bought an SSL certificate from a website and was able to make it work on my Apache server. As far as I know, it uses asymmetric keys and the private key is stored on the server while the ...
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0answers
73 views

How to calculate ϕ(n) from n?

I'm trying to fully understand all the steps of the RSA algorithm. I have clear so far that: $n$ comes from the product of two numbers: $p$ and $q$ The public key consists of the pair ($e$, $n$) ...
3
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1answer
99 views

Do equivalent RSA keys exist?

If $m^{ed} \bmod n = m$ for message $m$, public key $e$ and private key $d$, then adding any integer multiple of $n$ to $m^{ed}$ still equals $m$ modulo $n$. Supposing it exists, how do I find an ...
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0answers
19 views

How to prove a key generation protocol based on blind RSA signature?

It seems like that a user may use blind RSA signature to obviously generate a key. My design is as follows. Please correct me if I get anything wrong. (Please refer to WiKi https://en.wikipedia.org/...
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1answer
26 views

AEAD: Is it secure to decrypt the content encryption key before verifying the MAC?

The JSON Web Encryption (JWE) standard defines a number of encryption modes with the same basic form: First, the a unique content encryption key (CEK) is generated and used to encrypt the payload ...
3
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0answers
35 views

Computing cost for a trillionaire to compute GNFS in RFC 3766

RFC 3766, Section 4.1 discusses picking $n$ to achieve some target cost for employing the GNFS, i.e., $T$ is known and $N$ is unknown in the below equation: $$T = \kappa \cdot \exp{\left(c \cdot (\ln{...
3
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1answer
130 views

RSA: special parameters construction

I have to show that the following construction of $q$ allows to factorize $N$ : $p \in \mathbb{P}$, the set of primes $q \gets p \cdot \left((p - 1)^{-1} \bmod e\right) \bmod e$ $k=1$ while $q \not \...
8
votes
1answer
126 views

Could this “symmetric RSA” scheme provide key compromise resistant communications?

This question, and fkraiem's answer to it, made me wonder about the security and practicality of using "symmetric RSA" to provide a partially compromise-resistant secure channel. Specifically, assume ...
2
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1answer
117 views

Forgery attack against Textbook RSA with simple redundancy

I know how to forge vanilla Textbook RSA message signatures (easy). I've learnt that by adding a good redundancy to the message, it cannot be forged anymore. How can one add redundancy so that the ...
0
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1answer
57 views

What is proper size of window Using RSA Window method?

I want to Use Window method for RSA modular Exponentiation. because of SCA. But I don`t know what is proper window size.
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66 views

Feasible attacks on ECRSA cryptosystem

In ECRSA cryptosystem, I want to know the feasible attacks. For illustrations we have two prime $p$ and $q$ such that $p \equiv 2 \pmod 3$, $q \equiv 2 \pmod 3$ and generate key pair as follows: $$n = ...
2
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2answers
632 views

How do RSA and ElGamal key sizes compare?

I have a rather silly question regarding the comparison of RSA with ElGamal over integers. If you want to compare their performance in the same level of security, does the modulus of both of them need ...
3
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2answers
424 views

Any real world implementation using message recovery?

During my master thesis I came across RSA-PSS-R which is in my opinion a quite elegant way of saving bandwidth and space using digital signature. But I didn't find any information about any real world ...
0
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1answer
37 views

Do RSA keys contain a checksum mechanism? [duplicate]

I'm new to cryptography, and I was making an experiment a few minutes ago, but I want to have some deeper knowledge about RSA public and private keys. I have a set of keys One begins with ...
34
votes
5answers
6k views

In RSA, how does the CPU deal with this huge modulus (8192 bits)?

Whilst I understand how the RSA algorithm works, I don't understand how the CPU operates when it needs to use the mod function with a huge number $n$, for example. ...
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0answers
55 views

Why is RSA still being used? [duplicate]

In hybrid encrytion, I still see that some site's use RSA in their https connection, so now I wonder, why do they not use ECC instead of RSA, ECC requires less computational power and encrypt's and ...
2
votes
1answer
133 views

How does DH work when combined with ECC or RSA?

I know that Diffie-Hellman is used to create keys in a secure way over an insecure channel. But there is one thing which I cannot understand: I see that a lot of sites use ECC or RSA alongside DH. ...
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1answer
64 views

Questions about length key of RSA 2048 bit

I use putty gen to generate RSA key, I choose length of key is 2048 bit, it generate public key: ...
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24 views

Diffie-Hellman combined with DSA/RSA

we have learned Diffie-Hellman, RSA and DSA (Digital Signature Algorithm) in university. Because DH is vulnerable of Man-in-the-Middle we had the task to program the DH combined with RSA to protect ...
0
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1answer
33 views

factorization of an integer $N$ that is in special format

Suppose $p_0$ and $q_0$ are known prime numbers and define $p_i$ and $q_i$ as follows: $$p_{i+1} = next\_prime(p_i^2 + q_i^2), \qquad i \ge 0$$ and $$q_{i+1} = next\_prime(2p_iq_i), \qquad i \ge 0$$ ...
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33 views

Are public key and private key exchangeable? [duplicate]

If I get a key pair from RSA algorithm, can I make Private-Key public, and keep Public-Key secret without breaking the security of encryption and signature?