184
votes
Accepted
Can simply decompressing a JPEG image trigger an exploit?
Is there such a thing?
Absolutely. Feeding malicious input to a parser is one of the most common ways of creating an exploit (and, for a JPEG, "decompression" is "parsing").
Is this description ...
- 72.4k
88
votes
Are 7-Zip password-protected split archives safe against hackers when they are password-protected a couple of times?
First of all, that multi-encryption scheme is ridiculous.
The algorithm used by 7-Zip is AES-256 which is considered secure. But if someone would find a flaw in it which would make it breakable, then ...
- 49k
53
votes
Can simply decompressing a JPEG image trigger an exploit?
Agreeing with others to say yes this is totally possible, but also to add an interesting anecdote:
Joshua Drake (@jduck), discovered a bug based on a very similar concept (images being interpreted by ...
- 1,170
40
votes
Is compression mandatory with TLS?
Compression is not mandatory in TLS. And in modern libraries or products, it is often disabled by default because of possible attack vectors like CRIME which rely on TLS level compression.
Notably ...
- 191k
38
votes
Are 7-Zip password-protected split archives safe against hackers when they are password-protected a couple of times?
This is over engineering on a scale I've never seen. This is a BAD THING ™ because it increases the complexity of your solution without adding any security benefit.
The encryption mechanism is either ...
- 10.2k
28
votes
Are 7-Zip password-protected split archives safe against hackers when they are password-protected a couple of times?
First off, breathe. Encryption efforts often fails if you forget to breathe. Something about going unconscious causes us to have a hard time encrypting things!
Second, it sounds like you are in ...
- 9,216
17
votes
Is gzipping content via TLS allowed?
I read that this should be avoided because of CRIME/BREACH attack, is this correct?
It depends.
The CRIME attack is already mitigated in current browsers in that they don't use TLS compression and ...
- 191k
16
votes
Which encryption algorithm allows for the less output data than source data?
Encrypted data should be indistinguishable from random noise. Random data cannot be compressed. Therefore, compress data first and then encrypt it.
- 2,681
14
votes
Accepted
Does it weaken the encryption of SSH to use compression?
Compression before encryption is a problem if the attacker can control parts of the transferred data and then use the detectable compression ratio (i.e. amount of transferred data vs. original data) ...
- 191k
13
votes
Can simply decompressing a JPEG image trigger an exploit?
Unrealistic? There was recent critical bug in font definition parsing: https://technet.microsoft.com/en-us/library/security/ms15-078.aspx and libjpeg changenotes are full of security advisories. ...
- 271
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 ...
- 191k
12
votes
Which encryption algorithm allows for the less output data than source data?
No, what you are trying to accomplish is impossible.
Encryption tries to keep information confidential. For this it takes one input message out of all possible input messages and encrypts in such a ...
- 4,613
10
votes
Accepted
Brotli compression for HTTPS
support the new Brotli compression algorithm over HTTPS only.
In theory yes. In practice Chrome will currently accept brotli compressed answers with plain HTTP too, even though it does not announce ...
- 191k
10
votes
Is compression mandatory with TLS?
Compression is not required, and support for it is up to the implementations on client and server. Not all servers or clients support it (it is mandatory to support uncompressed traffic).
Some ...
- 43k
9
votes
Accepted
Security of decompression tools
How safe is it to decompress untrusted files
Just looking at the CVE's for unzip you will find several possible code executions, modifying the permissions of existing files, overwriting arbitrary ...
- 191k
9
votes
How sensitive are acoustic side-channels to compression with a narrowband codec?
According to Wikipedia:
"... G.711 passes audio signals in the range of 300–3400 Hz and
samples them at the rate of 8,000"
Nyquist criteria limits the top frequency to be less than half ...
- 7,973
6
votes
Accepted
Encrypted password inside compressed archive
The password is required to decrypt the archive, so storing a copy of the password inside the archive would be pointless - anyone who could decrypt the archive already has the password.
The only ...
- 186
6
votes
Accepted
is g-zipping assets a security concern?
I've been pondering this and I don't think your networking department is justified in this opinion. It does all depend on your threat model, but given the threat model of "hacked content to slip ...
- 126k
6
votes
Accepted
Compression and Encryption against security issues
To exploit the compression, as in CRIME/BREACH, the attacker must perform a chosen-plaintext attack. In other terms, this means that the attacker must already have an exploit on your computer:
Either ...
- 10.2k
5
votes
Accepted
Decryping a RAR file with same password
RAR uses AES256 for encryptionsource, thus the question is whether AES is cryptographically resistant to a known-plaintext attack.
At present there is no known method that allows retrieving AES ...
- 9,139
5
votes
What are the implications of reversing hashes
Reversible hashes aren't compression
Even hashes which we can reverse cannot be used as a compression. Assuming that we could reverse sha256 wouldn't make current compression obsolete, because there ...
- 8,389
5
votes
Accepted
Encryption and Compression
There's no contradiction here as long as you consider the issue in probabilistic terms. For example:
The reason I'm confused is that I thought that all encryption was supposed to do is make it as ...
- 10.4k
5
votes
Accepted
What steganographic techniques can I use in images that survive lossy compression?
Yes there are, the techniques are often used more for watermarking but can also be used for steganography.
One such technique is placing messages in frequency space via a 2-D Fourier Transform. ...
- 7,973
4
votes
Encryption and compression of Data
Neither:
Compress during encryption with an encryption tool designed to do both securely, such as GPG/OpenPGP.
This is basically Thomas Pornin's answer just more direct, so readers in a hurry don't ...
- 161
4
votes
With BREACH attack, is session-based CSRF token still secure?
If your site is vulnerable to BREACH, an attacker can guess anything in the body of the response one character at a time. The attacker does multiple requests, one per guess, and can see if he guessed ...
- 28.9k
4
votes
Are 7-Zip password-protected split archives safe against hackers when they are password-protected a couple of times?
I'm not as familiar with 7-Zip to fully understand its capabilities. However, assuming it is only a password-protected zip file, then no, this is not secure. However, I see some comments where 7-Zip ...
- 381
4
votes
Accepted
SSL/TLS compression attacks on mail servers (smtp)
Compression attacks like CRIME and BREACH work by triggering repeated transmission of almost the same message with only slight modifications, with these modifications controlled by the attacker. By ...
- 191k
Only top scored, non community-wiki answers of a minimum length are eligible