82
votes
Accepted
Why would an encrypted file be ~35% larger than an unencrypted one?
Most likely, the encrypted file is base64 encoded which would account for 33.3% file increase (you encode three bytes of data in four bytes of base64 data). Inserting a new line every 64 characters ...
- 39.2k
81
votes
Accepted
What is the attack scenario against which encrypted files provide protection?
File-level encryption can be useful in several cases, here's a few examples:
Sending data over insecure channels. You mentioned TLS, and that's enough when you have it. But what if you aren't sure ...
- 15.7k
67
votes
Accepted
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 ...
- 2,640
64
votes
Do Veracrypt encrypted volumes have any kind of brute force protection?
Any encryption is vulnerable to brute force attack, for example AES-256 has 2^256 keys, and given enough hardware we can “easily” brute force it. The problem is that there’s not enough silicon on ...
- 1,759
54
votes
Accepted
What security scheme is used by PDF password encryption, and why is it so weak?
There are two types of PDF protection: Password-based encryption and User-Interface restrictions. You are describing the second type of protection, namely the missing permission to copy-and-paste, to ...
- 1,053
52
votes
Strongest file encryption available
The strongest possible way to encrypt data is to start with a threat model. What sort of adversary are you trying to protect your data from? What are they willing to do to get it? All reasonable ...
- 9,226
47
votes
Accepted
Not understanding why I should use public/private key encryption over password?
The two options are intended for different use cases.
Option 1 is intended for your use case. It encrypts the file with a key derived from a password, so that only the person who knows the password (i....
- 11.5k
37
votes
Accepted
Is there any reason I shouldn't make a GPG-encrypted file publicly-accessible?
There is always a risk that any given cipher will be broken at some point and data like this will become truly public. So yes there are some risks but it doesn't mean you aren't making a reasonable ...
- 14.2k
32
votes
Strongest file encryption available
If you want the strongest, I’d suggest a one-time pad to encrypt the file.
If you want realistic, I suggest you rather expand on what your threat model is and take advice as to the actual level of ...
- 429
29
votes
Accepted
Downloading a file from a server with a secret: in text or binary?
There isn't really a difference.
If you use proper TLS encryption, neither can be read by a man in the middle, and if the server properly authenticates requests, nobody who is not allowed to will be ...
- 29.4k
28
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 (...
- 10.5k
24
votes
Accepted
Is it possible to read a text file inside a password-protected zip file without the password?
No. There are two ways of zip encryption, a classic one, which is weaker, and a newer one based on AES.
In both cases the password is needed in order to decrypt the contents (i.e. it's not just UI, ...
- 18.6k
22
votes
Do Veracrypt encrypted volumes have any kind of brute force protection?
Didn't veracrypt creators know about this issue?
(Not having brute-force protection)
As Andrew Morozko notes in his answer, they have addressed this – as far as it is possible – by using a ...
- 1,176
22
votes
Not understanding why I should use public/private key encryption over password?
There's one advantage of using public key cryptography over private key cryptography when you're encrypting file for yourself.
When you use symmetric cryptography, you need to expose the password ...
- 31.3k
21
votes
What security scheme is used by PDF password encryption, and why is it so weak?
The main problem with password-protecting a PDF file with a password is that you are basing the security on a password, which is some piece of data that a human user, somewhere, came up with in his ...
- 325k
21
votes
Would it be plausible to write your own anti-crypto-ransomware tool?
Why there are not already more anti-crypto-ransomware tools?
Because there are. They are called virus scanners and they should have heuristic algorithms to detect this behavior. Unfortunately the ...
- 49.2k
19
votes
Is ccrypt 'AES 256' file encryption fundamentally flawed
Password-based encryption is inherently vulnerable to dictionary attacks. Indeed, when you have the encrypted file, you can always try to decrypt it (or parts of it) with a given password and see if ...
- 325k
16
votes
Strongest file encryption available
I know nothing about cryptography. How do we encrypt a file in strongest (emphasis added) possible way such that we can access them some years later. I prefer that it should be fairly resistant from ...
- 4,981
15
votes
Is it possible to use SSH agent for generic data encryption?
It is not possible to use the SSH Agent to asymmetrically decrypt data that was encrypted with the public key because the SSH Agent only exposes the ability to sign using the private key, not decrypt.
...
- 291
15
votes
How to prevent illegal file transfer or copying of video files from a PC?
As you state in the question, doing this in a foolproof way is technically impossible. For the video to be displayed on the screen it must somehow reside somewhere in the RAM on the computer, be ...
- 65.3k
14
votes
Accepted
Are MySQL's database files encrypted?
Are MySQL database files that are stored on disk encrypted?
No, they are not.
You can (relatively) easily test this by moving .ibd or .myd files to a different system, where you can still read them....
- 29.4k
14
votes
Keep encrypted files in sync on a cloud service, without having to upload an entire encrypted volume each time
this would mean, obviously, re-uploading the single volume every time even the smallest file in it changes;
It is clear that this rules out, for different reasons, VeraCrypt or EFS.
That's not true. ...
- 9,149
14
votes
Why would I ever use AES-256-CBC if AES-256-GCM is more secure?
CBC is older, which means more compatibility and just overall historical reasons.
There are performance advantages, if you don't need GCM for authenticity. You often may want your own system for ...
- 7,848
14
votes
What is the attack scenario against which encrypted files provide protection?
Full disk encryption provides no protection whatsoever against attacker with remote access while your machine is powered (as by definition FDE requires data to be decrypted on every access). So in ...
- 2,285
13
votes
Encrypted password inside compressed archive
File compression utilities like Winrar or ZIP or 7zip encrypt the password and store it inside the archive.
I don't know where you got this information (claims without source are always bad) but I'm ...
- 196k
13
votes
Accepted
Does File-Based Encryption offer comparable security to Full-Disk Encryption on Android?
Full Disk Encryption (FDE) systems (like Truecrypt, BitLocker and FileVault) encrypt disks at the level of disk sectors. This is an all-or-nothing approach, since the encryption drivers won’t ...
- 8,879
12
votes
Is EncFS secure for encrypting Dropbox?
As tylerl and user80945 already said, using EncFS in a Dropbox is not secure. More information can be found in this article.
An alternative would be CryFS.
It is a new open source project that doesn'...
- 239
12
votes
How to prevent illegal file transfer or copying of video files from a PC?
Do not roll your own DRM scheme. The industry have tried and failed so many times that a homebrew solution will stand little chance.
It would be better to "stand on the shoulders of giants" and use ...
- 3,946
12
votes
Downloading a file from a server with a secret: in text or binary?
No,
If the type of file is specified then there is no added security at all. For example, unzipping a file is so trivial that it doesn't add any security.
If you ask whether it's more secure to ...
- 6,971
Only top scored, non community-wiki answers of a minimum length are eligible