Hot answers tagged

226 votes

Why can't the FBI read the key embedded in the iPhone's secure chip/ROM directly from hardware (silicon)?

Yes, it is possible. However, that runs the risk of destroying the device without getting the data off first, which is undesirable. It also does not achieve the political goals of forcing Apple to ...
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115 votes

Will quantum computers render AES obsolete?

Quantum computing will change the encryption game, but it is not yet clear how much it will change. It's not clear because we are not yet certain what sorts of problems quantum computers can solve. ...
  • 9,206
103 votes

Why has the NSA had a hand in deciding on encryption standards?

The NSA is a composite organization, that comprises several sub-entities called "directorates" with various scopes and goals. The NSA, as a whole, is supposed to have a multitude of roles; its signal ...
94 votes

Why can't the FBI read the key embedded in the iPhone's secure chip/ROM directly from hardware (silicon)?

What makes you think that they haven't already? This case is about setting a precedent to obtain access whenever the government desires. They chose this case because America's fear of terrorism will ...
  • 1,783
85 votes

Is it safe to use Dropbox in its present state?

It does not matter much how the data are encrypted as long as the owner of the data is not the only one in control of the encryption key. This in effect means that data encryption and decryption ...
78 votes

Why can't the FBI read the key embedded in the iPhone's secure chip/ROM directly from hardware (silicon)?

It doesn't scale While the general consensus is that such technology exists and would be available to FBI, it's not an appropriate general solution because it might be applicable to this case but (...
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72 votes

How is WhatsApp sending end-to-end encrypted messages in push notifications?

WhatsApp could be using VOIP background mode along with PushKit for solving this problem. Voip pushes are: delivered directly to the app. considered high-priority notifications and are delivered ...
71 votes

Use multiple computers for faster brute force

Sure it's possible, but it doesn't really help. The number of possibilities is just too large. Consider that a 256-bit key has 2256 possible values. That's 12✕1076, or 12 followed by 76 zeroes. If we ...
60 votes

Why would I ever use AES-256-CBC if AES-256-GCM is more secure?

CBC and GCM are quite different. Both are secure when used correctly, but CBC isn't as parallelizable and lacks built-in authentication. Due to this, CBC is only really practical for encrypting local ...
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57 votes

Encrypting text file with AES 256 instead of password manager

Considering those compromises you mention, do you think that encrypting files yourself will be easy? How do you know you won't get into those same pitfalls that resulted in compromises of password ...
47 votes

Encrypting using AES-256, can I use 256 bits IV?

The IV depends on the mode of operation. For most modes (e.g. CBC), the IV must have the same length as the block. AES uses 128-bit blocks, so a 128-bit IV. Note that AES-256 uses a 256-bit key (hence ...
45 votes

Do I need to use TLS if data is already encrypted and gets decrypted client-side?

You should serve this data over HTTPS regardless. As Gh0stFish pointed out, you can simply use an S3 bucket policy to require this. There are a couple reasons for this: Using plain HTTP makes it ...
  • 7,873
43 votes

Pseudorandom vs. True Random

There is a (common) misconception in this question that there is such a thing as “true” randomness and that this matters for security. In fact, whether “true” randomness exists is a philosophical ...
42 votes

How secure is 7z encryption?

7-zip (or any other similar utilities) encryption is designed to protect archived files. So, as long as the tool designers did their job well, you are safe for the second case (somebody getting his ...
40 votes

Use multiple computers for faster brute force

I did a calculation on this one once. Let's assume AES can only be broken using brute force. Clearly we are going to need a counter, which counts from 0 to 2256-1, and on average it will need to ...
  • 9,206
35 votes

Is this RSA/AES combination good?

All of the weaknesses in your protocol can be summed up as "use SSL" or even "use SSL, dammit !". In more details: All the protocol is of course vulnerable to impersonation, specifically the double ...
35 votes

What is the difference between JWT and encrypting some json manually with AES?

JSON Web Tokens (= JWTs) are based on the RFC 7519 and all differences will be extensively described there. If you take a look at this, you will see, that they are much more than what you seem to have ...
  • 7,913
35 votes

Can I recover a lost AES key?

Realistically, no you cannot. AES is very resistant to known plaint text attacks like most block ciphers. It's lucky you didn't lose any information and have the original database backup because your ...
  • 311
34 votes

Why does IV not need to be secret in AES CBC encryption?

I think it's easier to split this into its component parts, and consider them as separate entities: AES and CBC. AES itself does not "basically consist of XORing together chunks of the block" - it's ...
  • 132k
33 votes

Sql database password encryption opinion needed

No, this is not a good idea! As Lukas pointed out in an comment, you want to hash a password, never encrypt it! With your schema, it would be possible to get the plaintext passwords from an database ...
  • 5,903
30 votes

Client-server encryption technique explanation (TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 128 bit keys)

Asymmetric Cryptography There are two different parts to creating a TLS session. There is the asymmetric cryptography, portion which is an exchange of public keys between two points. Which is what ...
  • 12.3k
29 votes

Does the entire AES encrypted dataset have to be present to be 'cracked'?

You are doing it wrong. Not in the splitting or whatever; but in the thinking. AES encryption, if done properly, won't be "cracked". AES is the most robust piece in your system; this is the last part ...
  • 169k
26 votes

Why would I ever use AES-256-CBC if AES-256-GCM is more secure?

Big nitpick: GCM = CBC + Authentication. Nope, GCM = CTR + Authentication. But in general you are right; CBC is an older mode that was invented back in the dark ages cryptographically speaking (...
24 votes

Why did TLS 1.3 drop AES-CBC?

The problem here is not so much with CBC, but with alternatives that are easier to implement safely, without losing mathematical security.In fact, AES-CBC turned out to be notoriously difficult to ...
  • 4,793
23 votes

Calculate time taken to break AES key

One of my favourite gems on encryption is from Bruce Schneier in his book Applied Cryptography. One of the consequences of the second law of thermodynamics is that a certain amount of energy is ...
  • 721
23 votes

AES use same Nonce security risk?

When using AES-GCM, using the same nonce and key pair for multiple messages is catastrophic. You lose all of the security guarantees AES is supposed to provide. This is the worse possible scenario ...
  • 35.5k
21 votes

Can I use SHA-512 hash as AES key?

Technically, not as stated. AES-256 requires a 256bit key. SHA-512 will output 512 bits so unless you chop off half of the digest it will not work. A better solution is to use a standard and well ...
  • 2,348
20 votes

Extract AES key by comparing plaintext and encrypted data

No. This is known as a known-plaintext attack (or a chosen-plaintext attack if you are not only aware of but can select the plaintexts), and is a type of attack that AES is highly resistant to: there ...
  • 34.4k
20 votes

Why can't the FBI read the key embedded in the iPhone's secure chip/ROM directly from hardware (silicon)?

You are assuming the problem is technical. It might be political / legal. Let's assume the government already has the technical capability of extracting this information from phones, without Apple ...
  • 617
20 votes

How secure is AES-256-CBC with user provided password and initialization vector

My suspicion is: you're doing it wrong™. This is why I think so, from the top of my head: The variable holding the ciphertext is called hash. You are encrypting the user name. This looks like an XY-...
  • 14.3k

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