Linked Questions

0 votes
1 answer

Textbook RSA with exponent e=3 [duplicate]

I remember $e=3$ is a bad choice for textbook RSA. But I can't really recall why. What happens if I choose $e=3$? Can I retrieve the message by simply calculating $\sqrt[3]{c}$? Why can't I do that ...
stefanbschneider's user avatar
52 votes
5 answers

How to find modulus from a RSA public key?

I am studying the RSA cryptosystem. The public key consists of $(n, e)$, the modulus (product of two large primes), and the encryption exponent. I want to separate the modulus $n$ and exponent $e$. A ...
user3001408's user avatar
76 votes
1 answer

Can you explain Bleichenbacher's CCA attack on PKCS#1 v1.5?

I've studied that the Bleichenbacher's CCA attack on PKCS#1 v1.5. is a base to many versions of attacks in the area. I'm trying to understand that attack, but every explanation I saw starts with the ...
Bush's user avatar
  • 2,120
30 votes
9 answers

RSA with small exponents?

Just to establish notation with respect to the RSA protocol, let $n = pq$ be the product of two large primes and let $e$ and $d$ be the public and private exponents, respectively ($e$ is the inverse ...
Elliott's user avatar
  • 1,661
18 votes
5 answers

Is there a situation where RSA cannot be replaced with ECC + symmetric algorithms? If no, why do we still use it?

RSA is both an asymmetric encryption algorithm and a digital signature algorithm. However, in recent years, many cryptographic protocols (TLS, for example) have moved away from the use of RSA to ...
Luke Park's user avatar
  • 562
27 votes
2 answers

Why is PuTTYgen-created RSA public exponent(e) not in {3,17,65537}?

As far as I know, RSA public exponent(e) should be one of {3,17,65537}. However, I found PuTTYgen-created RSA public exponent(e) is 0x25(37) by default,as follows, (PuTTYgen version: 0.66) I am ...
Matt Elson's user avatar
6 votes
2 answers

Must RSA exponent and modulus be odd

I'm working on some RSA code that uses Toms Fast Math (TFM for short), and I'm trying to understand why the functions fp_exptmod (for modular exponentiation ...
ubiquibacon's user avatar
7 votes
2 answers

Is there a way to systematically calculate the public exponent $e$ in RSA?

I'm learning RSA in one of my classes and we were given a problem: $p = 5$, $q = 11$ I have done the following steps: $n = 5 \cdot 11 = 55$ $\phi = (5-1)\cdot(11-1) = 40$ I know that to find ...
orange's user avatar
  • 193
4 votes
3 answers

RSA: Is it secure to use the private key to encrypt and the public key to decrypt?

This may sound weird: What if I don't let others know my public key, then use my private key to encrypt, and the public key to decrypt? Is this secure? Let me explain a little bit: Common usuage: use ...
Gerry's user avatar
  • 113
9 votes
1 answer

RSA encryption and decryption with multiple prime modulus using CRT

Every information I found on internet about RSA-CRT encryption/decryption uses only two primes. I'm interested in my project in doing that using multiple (up to 8) primes. The general idea is to ...
tomQrsd's user avatar
  • 93
3 votes
2 answers

Key space vs Cardinality of 1024-bit RSA

I have been trying to figure out the encryption key space, and cardinality of 1024-bit RSA. From my understanding, the key generated from 1024-bit will be primes greater than $2^{1023}$ but less than $...
user3547551's user avatar
4 votes
3 answers

Openssl & RSA : how many public exponents are possible?

I would like to know if it is possible to set the public exponent we want with "OpenSSL RSA" or if it is really limited to 2 possible exponents: 3 65537 If yes, why ?
Arithma's user avatar
  • 43
10 votes
2 answers

In textbook RSA with low public exponent, how big does a random message needs to be?

Assume RSA with a public modulus $N$ of $n$ bits, a small odd public exponent $e$, plaintext $M$ a random non-negative integer less than $2^m$ for some integer parameter $m$, with $M\mapsto C=M^e\bmod ...
fgrieu's user avatar
  • 137k
2 votes
2 answers

RSA Key Generation Parameters - public exponent, certainty, string-to-key count

I want to know what values are appropriate for the public exponent and certainty when generating an RSA Key (for example using Bouncy Castle RSAKeyGenerationParameters function). What is the ...
user12903's user avatar
4 votes
1 answer

Bleichenbacher's Attack on high public exponent RSA keys?

Why can't Bleichenbacher's Attack work for RSA public exponents with values equal to 65537 and above? Does the fact that 65337 is a prime number have any relevance to it?
YoungBoul's user avatar

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