Linked Questions

16 votes
4 answers
2k views

Is there any reason someone wouldn't use a longer key?

Larger key sizes are said to be more difficult to bruteforce; is there any reason someone would then decide to instead use a smaller key? Is there any negative effect in using a larger key size, such ...
IQAndreas's user avatar
  • 6,845
15 votes
1 answer
19k views

Will double encryption increase the security of cipher vs bruteforce?

Assume I have a function encrypt(mes,key) where mes is the message, and key is the key. The length of key is 64 bits. Last but not least: assume the only way to crack my cipher is a brute-force attack....
Tomáš Šíma's user avatar
4 votes
3 answers
13k views

Brute forcing ssh keys

My problem is a common one: I deleted my SSH key, and forgot to set rm to point to a .trash file. I have the public key, and I need to get in this server. I am not doing this on anyone else's server. ...
StackExchange User's user avatar
15 votes
4 answers
5k views

Is there a length beyond which increasing password length provides no additional security?

Assuming that the password is stored hashed and salted, and that it is a string of random characters, is there a point where adding to password length doesn't add security? Since the hash will have a ...
Peter's user avatar
  • 253
9 votes
2 answers
9k views

Do you need more than 128-bit entropy?

UUID uses 128-bit numbers. Currently it is not feasible to randomly produce two UUIDs that are the same. Does that mean 128 bits of entropy is suitable for all cryptographic operations? I would ...
dodtsair's user avatar
  • 103
7 votes
3 answers
2k views

Why do we have such big keys?

In Chapter 7 of Applied Cryptography, Bruce Schneier claims that, due to thermodynamic limitations, "brute-force attacks against 256-bit [symmetric] keys will be infeasible until computers are built ...
KnightOfNi's user avatar
  • 2,277
15 votes
2 answers
25k views

Why does Google prefer ECDHE-RSA-AES128-GCM-SHA256?

I want to configure my new mail server secure as possible and wondering about the used cipher while connecting to Googles SMTP server. I'm curious why they prefer the cipher ECDHE-RSA-AES128-GCM-...
Ludwig Behm's user avatar
15 votes
2 answers
3k views

How can a passphrase with 256 bits of entropy practically be constructed & memorized?

Quoting Wikipedia: A password with, say, 42 bits of strength calculated in this way would be as strong as a string of 42 bits chosen randomly[.] Assuming that interpretation is correct, combined ...
user avatar
12 votes
3 answers
4k views

ProtonMail security concerns

This TED talk brought me here. First of all, to those who created ProtonMail: Nice job!!. Regardless of what people say, it's definitely a big step forward from tradition options like Hotmail, Gmail ...
icehenge's user avatar
  • 430
6 votes
2 answers
2k 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 right.)...
ro_m's user avatar
  • 71
13 votes
3 answers
1k views

Can signing too much compromise a private key?

Can a collection of many messages signed with the same private key be abused to either forge signatures so some (but not all possible) messages, or even worse to reconstruct that private key with less ...
Tobias Kienzler's user avatar
8 votes
3 answers
9k views

For how much time should I randomly move the mouse for generating encryption keys?

When creating a Truecrypt volume, there is the wizard page in which the user is told to randomly move the mouse (the longer the better) to generate entropy, and that it will significantly increase the ...
Benoit's user avatar
  • 523
10 votes
2 answers
1k views

Unseen.is encryption claims revisited with their proprietary, patented "xAES" algorithm

I had asked last year about the encryption claims by the web service called https://unseen.is. The very same service that had claims of "beyond army level encryption", "4096 bit keys" etc. This is the ...
Harry Greenwald's user avatar
10 votes
1 answer
9k views

PGP RSA key size - encryption/decryption time

From what I've read, PGP only uses the pub/priv keys for encrypting/decrypting a symmetric key used for actually encrypting/decrypting data. I'd reasonably assume that longer asymmetric keys wouldn't ...
raphael b's user avatar
  • 103
7 votes
2 answers
4k views

Are RSA 2048, ECDSA, and the SHA uncrackable in the sense that AES-256 is uncrackable?

The answer https://security.stackexchange.com/a/25392 has seemingly shown that AES-256 will not be directly cracked for at least the next 200 years (unless we manage to harvest the energy output of ...
cryptonamus's user avatar

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