Tagged Questions

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 performance

I was wondering what is the performance bottleneck in RSA algorithm? Is it the size of message, calculating the modular inverse, exponentiation? Say I have a fixed value of n to encrypt and decrypt ...
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Why is RSA encryption significantly faster than decryption?

I am designing an implementation of RSA . I recorded computation times in Java by using System.currentTimeMillis(). It returned an encryption time of 0.05 ms and ...
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Can the encryption exponent e be greater than ϕ(N)?

So I was just wondering in RSA, can the encryption exponent e be greater than ϕ(N)?? For an examples sake, lets just say N = 707, so p = 101 & q = 7. So, we have ϕ(707) = 600. Can I have e = 707?...
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RSA: Recover e given factorization of N and plaintext/ciphertext pair

Is there a way to recover the public exponent e (assume in this case it is in fact not public) used in an encryption if I know the following: Factorization of <...
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Avoiding overflow when encrypting with RSA

When encrypting with RSA one calculates $m^e \pmod n$ by doing the following: m^e % n Where $m$ is what we encrypt. Often $e$ is a very big number to make it ...
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What's the main difference between Pohlig-Hellman and RSA?

Both Pohlig-Hellman and RSA perform encryption and decryption by exponentiation modulo some integer ($p$ prime for PH, $n$ composite for RSA). They both use a key $e$ as the exponent to encrypt a ...
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Is RSA of a random nonce with no padding safe?

Consider the following protocol: Bob has a private RSA key $B_{priv}$, and Alice knows the public key $B_{pub}$. Alice wants to send confidential messages to Bob (no integrity intended). To send a ...
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Isn't the deterministic property of (EC)DSA a security problem?

From what I read in Wikipedia's article "Elliptic Curve DSA ~ Security", the "deterministic" generation of $k$ can help prevent certain type of attacks (such as the one happened to Sony). However, ...
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Textbook-RSA meet-in-the-middle attack against other RSA based schemes?

A “meet-in-the-middle” (not “man-in-the-middle”!) attack on textbook-RSA was presented to me. The only requirements for it was that the attacker gets the output of RSA and the public key, and that the ...
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Chosen plaintext attack on textbook RSA decryption

Let $(n,d)$ be an RSA private key and $(n,e)$ the corresponding public key. Generate a secret random $r$ from $(\mathbb{Z}/n\mathbb{Z})^*$ Compute $C’ = C (r^e) \bmod n$ Submit $C’$ as a chosen ...
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At what stage is DHE and RSA used during the SSL/TLS handshake?

At what stage of the SSL/TLS handshake is the DHE and RSA used and what is the purpose of using a pre-master secret when you could just use RSA to exchange the symmetric key (i.e. AES) for further ...
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RSA Key generation Public exponent too big

I'm currently writing a paper about RSA (a self-chosen subject). I'm writing about the key-generation in RSA, and I have problem finding the public exponent e. I have chosen p = 61 and q = 53. Then ...
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RSA Digital Signature vs Elgamal Digital Signature

What are the advantages of RSA signatures against ElGamal signatures? Is there a situation in which it would be better e.g. to use RSA signatures?
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Highest prime factor that is Safe for a particular scheme

My question is how many bits of prime number is secure so that it cannot be factored from very large number? Until today how large prime factor is found in large number? Quantum computing find ...
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Why is RSA usually limited to messages up to 1 block

I'm wondering why RSA encryption usually is only used for messages that fit into one block. For larger messages hybrid encryption in combination with symmetric ciphers like AES seem to be the solution ...
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I've been looking at the weakness with plain/textbook RSA, where the same message is encrypted and sent to multiple destinations. In this case, it is possible to recover the message. Given that an ...
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“Signing” with public key

For this question, the following caveats and assumptions hold: There exists a 2048-bit RSA key pair used exclusively for signing/verification The private key is kept completely private There exists ...