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Questions tagged [rsa]

RSA is a common public key algorithm, which can be used for encryption and signature. It is a core component of most the security protocols used on the Internet, including the SSL/TLS protocol suite.

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117
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4answers
104k views

Is there any particular reason to use Diffie-Hellman over RSA for key exchange?

I often see RSA being recommended as a method of key exchange. However, the Diffie-Hellman key exchange method appears to be secure as well. Is there any considerations one should take into account ...
88
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4answers
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Will quantum computers render AES obsolete?

This is a spin off from: Use multiple computers for faster brute force Here's at least one source which says that quantum computers are on the way to being able to break RSA in the not too distant ...
69
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2answers
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Why OpenSSH deprecated DSA keys

There was a question RSA vs. DSA for SSH authentication keys asking which key is better. Basically all answers were more in a favour of RSA over DSA but didn't really tell that DSA would be somehow ...
48
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4answers
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Why is key exchange necessary at all?

Let's say "Alice" and "Bob" want to communicate with each other over an insecure network. Using Diffie–Hellman key exchange, they can get the same symmetric key at last. However, as I understand, ...
47
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3answers
25k views

Can I get a public key from an RSA private key?

As far as I remember you encrypt the message using public key and decrypt it using private key. My question is whether it is possible to get a public key from an RSA private key. For example if I have ...
45
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2answers
16k views

Is it bad that my ed25519 key is so short compared to a RSA key?

I recently generated a new SSH key in the ed25519 format. The public key is only 69 bytes long while my old RSA key is 373 bytes. From my perception ed25519 is the more recent and secure format. So ...
42
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1answer
28k views

SSH Key: Ed25519 vs RSA

A lot of people recommend using Ed25519 instead of RSA keys for SSH. The introduction page of Ed25519 (http://ed25519.cr.yp.to/) says: [..] breaking it has similar difficulty to breaking [..] RSA ...
37
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5answers
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Encryption - should I be using RSA or AES?

My model is one where I have several clients which wish to speak with some (but not all) of the other clients. All messages will be sent through a server. Only the two clients communicating with ...
34
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1answer
5k views

How does OpenSSL generate a big prime number so fast?

In order to generate a 2048 bit RSA key pair, you need to generate two big prime numbers with 1024 bits length. As far as I know, OpenSSL chooses a random 1024 bit number and starts looking for a ...
31
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1answer
20k views

How many qubits are needed to factor 2048-bit RSA keys on a quantum computer?

I've been reading about quantum computing and turns out that 512-bit quantum processors are already a thing. I also read about Shor's algorithm, which can break RSA and several asymmetric encryption ...
28
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1answer
4k views

What are the odds of an RSA private key collision?

Given the various lengths of RSA key pairs (1024, 2048, 4096) what are the odds of two users having generated the exact same private key?
27
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2answers
64k views

RSA public key and private key lengths

I'm having a problem understanding the size of an RSA public key and its private key pair. I saw different key sizes for RSA algorithm (512, 1024,... for example), but is this the length of public ...
26
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5answers
75k views

RSA maximum bytes to encrypt, comparison to AES in terms of security?

What is the maximum number of bytes for encrypting a plaintext message using RSA that is reasonably secure and also efficient and would AES be better for the same size in bytes? The encryption doesn't ...
25
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4answers
6k views

Is a passphrase-protected SSH private key susceptible to a dictionary attack?

If I have a passphrase-protected SSH private key, AND if this passphrase is sufficiently random and long (say, 20-, 30-, 40-characters long, or even more!), AND if I make this private key of ...
24
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1answer
22k views

New PGP key: RSA/RSA or DSA/Elgamal?

I wanted to create a new PGP key using GPG Keychain Access on my Mac. One of the options was to choose keytype: RSA and RSA DSA and Elgamal RSA (Sign only) DSA (Sign only) I found this Superuser ...
23
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4answers
12k views

Why does PGP use symmetric encryption and RSA?

Looking into the details of Pretty Good Privacy, I'm confused as to the reasoning behind encrypting the message with a session key and the key with the recipient's public key via RSA. I fail to see ...
22
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1answer
18k views

Are SSH keys and PGP keys the same thing?

I have a 3072 bit RSA key that I generated for use with SSH. Can this key-pair be used with PGP/GPG, or do I need to generate a new pair of keys separately for use in email encryption? Are the two ...
20
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3answers
35k views

Key size difference between AES and RSA

Can I say that 128 bit using AES provide more security than 1024 using RSA?
20
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1answer
10k views

Relationship between RSA, Diffie-Hellman Key Exchange, PKI and X.509?

I am getting confused with RSA, Diffie-Hellman Key Exchange, PKI and X.509v3. I took a look of RSA's mathematics algorithm, it seems like a encryption algorithm, right? Generating public key and ...
20
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1answer
15k views

How does SSH use both RSA and Diffie-Hellman?

SSH protocol 2 allows you to use DSA, ECDSA, ED25519 and RSA keys when establishing a secure connection to a server. (Keep in mind for this question that I'm only familiar with the procedure and ...
19
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3answers
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How do RSA SecureID ® Keys Work?

I have been using RSA SecureID ® Keys for quite some time now (perhaps 10 years), for things such as securely my home banking account online or accessing my company's network of computers from home. ...
18
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3answers
24k views

Which host key algorithm is best to use for SSH?

When you first connect to an SSH server that is not contained inside your known_hosts file your SSH client displays the fingerprint of the public key that the server gave. I found from this question ...
17
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2answers
1k views

RSA key recovery using sound - How does it work?

A very interesting Debian security advisory was released yesterday. Genkin, Shamir and Tromer discovered that RSA key material could be extracted by using the sound generated by the computer ...
14
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2answers
53k views

Decrypt from cipher text encrypted using RSA

I am sniffing a client side application traffic and I found some encrypted data. I am not able to decrypt it. Information which I have is Public Key: ...
14
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1answer
7k views

What is RSA OAEP & RSA PSS in simple terms

After googling or youtubing, i still cant find any information on RSA OAEP & RSA PSS. Can someone explain it in simple terms to me? I understand RSA is public key and private key. Why is there so ...
14
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2answers
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Why is ECC more vulnerable than RSA in a post-quantum world?

Forgive me if this should be in the crypto sub, but sometimes the answers there are very mathematical and I would rather have an answer which is a bit lighter on the math. I was watching the ...
13
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2answers
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Converting ECC Private key to PKCS#1 format

Is there any way to convert an ECC private key to RSA PKCS#1 format? I have tried converting it to PKCS#8 first using OpenSSL: openssl pkcs8 -topk8 -nocrypt -in EC_key.pem -out pkcs8_key.pem This ...
13
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3answers
1k views

Can RSA keys be swapped?

On a theoretical level, is there anything inherently different about public vs private keys? During RSA key generation there are two keys generated, key A and key B. Key A is private and Key B is ...
13
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2answers
2k views

DNSSEC signing algorithms

Virtualmin supports a flurry of algorithms for DNSSEC: RSASHA1, RSASHA256, RSAMD5, DSA, DH, HMAC-MD5(???), NSEC3RSASHA1, NSEC3DSA. If I understand correctly, there's Proof of Concept available for ...
13
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2answers
1k views

Why are the gitlab SSH host key fingerprints not matching?

I tried to log into my university's gitlab via SSH. As expected, I was warned that the host is not known. Therefore, I tried to find the SSH host key on the "current configuration" page in the manual. ...
12
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2answers
2k views

Can I determine a private key given the encrypted data and corresponding cleartext?

If I know that Data A is an encrypted form of Data B is that sufficient information to determine the private key?
12
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2answers
1k views

Does it matter which key is considered private and which public?

Mathematically, is there a difference which set of characters is private_key and which one is public_key? @Edit At the moment of asking I was thinking on RSA, not asymmetric crypto in general.
12
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2answers
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Trying to understand RSA and it's terminology?

I get the gist of RSA but I'm mostly self taught so sometimes the phrases I picked to describe something don't match up with the widely accepted terminology. I'm trying to remedy this. I'm working ...
12
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1answer
569 views

Recommended operational security for generating one's primary key pair?

I have been looking for an operational security guide for generating one's asymmetric key pair for (Open)PGP. I have found plenty of technical guides for how to use GnuPG to generate RSA key-pairs, ...
11
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5answers
7k views

Is this RSA/AES combination good?

The team of developers I am part of is trying to develop a safe way to exchange sensitive data between a server and mobile devices. We have come up with the following algorithm: Device generates ...
11
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4answers
10k views

What is the role of RSA in ECDHE-RSA? [duplicate]

I have read some textbooks and not found a convincing explanation. In the cipher suite ECDHE-RSA-AES128-GCM-SHA256, what is the role of RSA in the first part (ECDHE-RSA)? This part of the cipher ...
11
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1answer
5k views

Should SHA-1 be used with RSA-OAEP?

PKCS#1 defines SHA1 as a default hash function and all implementations support this hash function and the mask generation functions based on SHA1. In some implementations you can change the hash ...
11
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2answers
4k views

Generate new key - ECC vs RSA

I intend to start using GnuPG again. I haven't used it for the last 2 years and was surprised that there is now the option for RSA and ECC keys. After reading a bit about ECC, it seems to me there is ...
11
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0answers
492 views

Strength and length of Symmetric vs Asymmetric keys [duplicate]

There are many questions surrounding the differences between symmetric and asymmetric encryption keys. I think I've read them all at this point. But I'm still left wondering: Why does a "secure" ...
10
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3answers
6k views

RSA key length vs. Shor's algorithm

I have just read a passage in Zeilinger's book about quantum world. My question is: Suppose there exist quantum computers. Given that a quantum computer can use Shor's algorithm, what key length ...
10
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2answers
14k views

1024-bit DHE vs 2048-bit RSA

Currently with apache/mod_ssl, if DHE is enabled then a 1024-bit ephemeral key will be used. I found the following quote in Adam Langley's blog: Ideally the DH group would match or exceed the RSA ...
10
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1answer
5k views

When exactly is Diffie-Hellman used in TLS?

I'm aware that Diffie-Hellman is a key exchange algorithm whereas RSA is an asymmetric encryption algorithm. I have the following questions: During TLS handshake, will both RSA and DH be used? (I ...
10
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1answer
7k views

PEM, CER, CRT, P12 - what is it all about?

I hope my question is not too general, but I find the topic of storing asymmetric keys very confusing.. Here's how I understand it: Using openSSL I can generate my RSA keys pair: openssl genrsa -out ...
10
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1answer
16k views

What are the differences between the RSA, DSA, and ECDSA keys that ssh uses?

In my /etc/ssh/ directory, I can see three that I have three different types of ssh keys: -rw------- 1 root root 607 Oct 4 22:43 ssh_host_dsa_key -rw-r--r-- 1 root root 623 Oct 4 22:43 ...
10
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1answer
9k views

ssh-keygen: What is the passphrase for?

When using ssh-keygen: What is the passphrase for? Why is it optional? What are the security implications of specifying (or not specifying) one? Below is an excerpt taken from a shell session (...
10
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1answer
2k views

Manually walking through the signature validation of a certificate

Since I am not too familiar with the Web of Trust and Public Key-Infrastructure I decided to learn about it by following the signing chain of a X.509 certificate issued to CN=*wikipedia.org (Serial ...
10
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1answer
72k views

How to check a public RSA key file is well formed? [closed]

Inside a shell script I want verify a public RSA file. I want to find a way to check if this file is a genuine public key file, nothing else. What are the ways I can verify this input file to check ...
9
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1answer
33k views

Shall I set “RSAAuthentication yes” in sshd_config if I use only ECDSA key?

In a context of proprietary client boxes and servers, I want to limit authentication to ECDSA keys. Historically, "RSAAuthentication yes" was used to enable authentication with RSA and maybe DSA keys. ...
9
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1answer
4k views

zero knowledge proof - where do we use it?

zero knowledge proof, Where do we use it online? I thought we mostly use the RSA algorithm.
9
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2answers
22k views

Ways to generate symmetric and asymmetric keys

We are using Beaglebone Black based custom board, and want to use hybrid encryption for encrypting firmware file, i.e. symmetric for encryption big firmware file and asymmetric for encrypting ...