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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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 ...
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1answer
2k 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?
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539 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 ...
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3answers
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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 ...
11
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1answer
173 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 SHA1 ...
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4answers
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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 ...
9
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2answers
1k 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?
7
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3answers
230 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 ...
7
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651 views

Is it possible to prove which public key was used to encrypt a message?

Pretty much the title: If Alice sends a message to Bob that she encrypts with Bob's public key, is it possible for Eve to prove that the ciphertext was encrypted with Bob's public key, that the ...
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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 ...
6
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3answers
536 views

Lessen impact of DoS attack on cpu-expensive login?

This is a follow-up to my previous question: Prevent DOS against RSA authentication. This question is also discusses a similar problem: Prevent denial of service attacks against slow hashing ...
6
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3answers
288 views

Is generating an RSA key with password and then stripping it off more secure than no password at all?

Some time ago I came across this question on SO; it asks how to remove the passphrase from an existing RSA key using a PHP equivalent to the existing openssl rss command. I've posted an answer with ...
6
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2answers
181 views

Should I test my SSL certificate for “RSA Shared Primes” before using it?

There are several papers from 2012 that say it's possible to factor several moduli by factoring shared primes. The link above includes python sourcecode to verify and test for this fact. Given this ...
5
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2answers
716 views

Designing a cryptographic file-sharing protocol

As a learning project, I am trying to implement a secure way to share files with a friend over dropbox. (I am not looking for existing software, I am doing this in order to learn how to do this ...
5
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5answers
8k 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 ...
5
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2answers
1k views

Web & insecure HTTP - Using RSA for encrypting passwords on the client side

I used client side password hashing in my register and login project. Its purpose is to prevent passive adversaries/eavesdroppers from discovering users' plaintext passwords when HTTP requests are in ...
5
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2answers
173 views

Security sanity check

A company whose services I'm trying to integrate uses this protocol: An AES key is embedded in an Android library. To authenticate itself, the library sends a SHA1 hash of the key over plain HTTP. ...
5
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1answer
680 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.
5
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1answer
87 views

What is the impact of RSA key's size on CPU load?

I use ssh connection encrypted and compressed. If I use small RSA keys or very big RSA keys, what is impact on CPU load for compression, for decompression and on bandwidth (encrypted file size) ?
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3answers
2k 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 ...
4
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4answers
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What is the easiest way for a newbie to RSA to create & use a key pair on Windows?

So I need to get a block of text sent to me over email from a friend, but before he sends it he wants a public RSA key from me. Am wondering what is the simplest way for me as a newbie to generate ...
4
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1answer
818 views

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 but still strong on the tech ...
4
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1answer
123 views

Public keys without the certificates

There are two clients and a server. Each client generates an RSA key pair and uploads public key to the server. The server associates the public key with the user identifier that is specified during ...
4
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2answers
129 views

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 ...
4
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1answer
608 views

Do I need to keep certificate signing requests and public keys?

I've created an RSA key. Created a CSR. Got it signed and now I have my certificate. It's for a webserver running https. The public key can be generated from the private key, so I guess I don't need ...
4
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1answer
277 views

RSA vs PBKDF2 for password storage (theoretical)

I know this is not the right way to store passwords, but I'm asking this from a theoretical perspective: Suppose a web site's passwords were encrypted with RSA asymmetric encryption and the private ...
4
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2answers
267 views

Prevent DOS against RSA authentication

In my current setup, the clients are bundled with the server's public key. The client encrypts a nonce and sends it to the server which uses its own nonce and the nonce received from the client to set ...
4
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1answer
88 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, ...
4
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2answers
251 views

Security of PGP for Long-Term Storage

How secure are PGP/GPG encrypted mails? I realize that it's probably fine for regular e-mail scenarios, but what about the security over longer time periods (>30 years)? Is the 4096 bit limit for ...
3
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1answer
689 views

Are there any holes in this security design?

This design is for transport security between a client and a server. I'm planning on using it for a cloud storage system. I would like it to be secure against you-know-who. I'm trying to prevent the ...
3
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2answers
144 views

Deciding whether to sign someones key

How do i decide whether to sign someones PGP public key? I was looking at some contact pages and they have a request for people to sign their public key. How serious of a commitment is it to sign ...
3
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4answers
472 views

How can we trust PKI, for example, Verisign?

We want to send an encrypted message to Alice. We can ask her a public key over the network, encrypt with it a message and send that message back. It is bad, because someone can pretend to be Alice ...
3
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2answers
4k 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: ...
3
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2answers
6k views

Key size difference between AES and RSA

Can I say that 128 bit using AES provide more security than 1024 using RSA?
3
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2answers
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Isn't this the same as using a certification authority?

Taken from Wikipedia, here is the pretext to my question: A certificate authority (CA) is an organization that stores public keys and their owners and every party in a communication trusts this ...
3
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1answer
333 views

Is TLS 1.0 sufficiently secure for a bank?

I disabled SSL2 and SSL3 in my Firefox browser, version 24. I only enabled TLS 1.1 and 1.2. Unfortunately when I went to my bank's website, I found that it didn't work until I re-enabled TLS 1.0. ...
3
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1answer
170 views

How to fix this broken crypto protocol?

I am considering a protocol where you upload a one time pad to a server, using public key encryption and then the result (using the pad) is sent back in plaintext: Alice uses Bobs RSA public key to ...
3
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1answer
2k views

Certificate verified using two different paths

StartSSL has an intermediate certificate that they use to sign their EV certificates: sub.class4.server.ca.pem. This certificate's issuer is shown by openssl x509 to be /C=IL/O=StartCom ...
3
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1answer
173 views

Javascript client side image decryption, does this add any safety or is it flawed

I want to store passport copies safely in a database, the database itself is a normal MySQL database and on a somewhat trusted web server. The user who owns the passport copy should only be able to ...
3
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2answers
193 views

Verifying the authenticity of a public key without manual intervention?

In RSA encryption it is said that ensuring the authenticity of the public key can be as important as the protection of the private key. An effective way of doing this is to have key custodians ...
2
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2answers
169 views

Was DSA invented from RSA?

I'm wondering if the two algorithms are similar and whether DSA was really just based off RSA? Is DSA based on RSA and public key encryption? If so how does DSA introduce signing and makes it ...
2
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2answers
567 views

Why should the dh keylength match rsa length in tls?

A few sources state that the DH keylength (bits of the prime) should match the keylength of rsa for TLS. For example SSL_set_tmp_dh(3) from openssl has example code on how to match the dh parameters ...
2
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4answers
366 views

how secure is rsa encryption for a web login without https?

I have a server running rstudio. This is basically a web application, and it is currently only accessible over the local network. The web app takes your Linux username/password in order to log you ...
2
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1answer
874 views

Is my RSA signed data secure?

So with all of the FUDD (fear/uncertainty/doubt/disinformation) going around about RSA in light of Snowden leaks and other discoveries about backdoors into PRNG, I'm uncertain what this means to me... ...
2
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3answers
963 views

Any alternative available for RSA? Is the web still visible to NSA?

After the Snowden revelations, is there any mass change being carried out to HTTPS protocol? As far as I understood, any HTTPS communication is still visible to NSA as they can compromise the RSA ...
2
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2answers
233 views

For DHE_RSA_.. Cipher Suites what is RSA used for?

In addition to achieving PFS with DHE, we want as little as possible to be revealed when the server's private key is revealed. So, what is RSA used for in DHE_RSA cipher suites? What does the server ...
2
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4answers
157 views

How is security of server's RSA private key is ensured?

We repeatedly hear news of hacking of passwords from PW database (server side) but nothing about hacking of server's RSA private key (not asking regarding finding p and q for a given public modulus ...
2
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1answer
231 views

openssl ECDHE-RSA… cipher suite selected while using RSA server cert and ECDSA client cert

The scene: s_server using RSA certificate. s_client using ECC-ECDSA certificate. Client authentication is required (option -Verify set on s_server) Cipher-suite selected after handshake is ...
2
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1answer
122 views

How secure is PKCS #12

I need to move user cryptographic identity between several user devices. In the operating system I have only one option: use password-protected PKCS #12 to import the identity to the OS secure store. ...
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3answers
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How much time / “entropy collected” should generating a RSA 2048bit keypair take?

The purpose of my question is get an better idea about reasonable amout of time the generation of the RSA public/private keypair should take? To be less vague let me specify the question and define I ...