the act of compression reduces the size of the file(s) being compressed by encoding information and eliminating statistical redundancy.

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85
votes
5answers
10k views

Can simply decompressing a JPEG image trigger an exploit?

The novel Daemon is frequently praised for being realistic in its portrayal rather than just mashing buzzwords. However, this struck me as unrealistic: Gragg's e-mail contained a poisoned JPEG of ...
42
votes
1answer
17k views

Does WinRAR leave traces of temporarily extracted files?

If I have an encrypted RAR file which will only open using a password, and I opened a file directly from within WinRAR by double clicking the file inside WinRAR, I assume that WinRAR will create a ...
30
votes
4answers
10k views

BREACH - a new attack against HTTP. What can be done?

Following on from CRIME, now we have BREACH to be presented at Black Hat in Las Vegas Thursday (today). From the linked article, it suggests that this attack against compression will not be as simple ...
22
votes
3answers
16k views

Encryption and compression of Data

If we want both encryption and compression during transmission then what will be the most preferable order. Encrypt then compress Compress then encrypt
11
votes
4answers
2k views

Is it safe for GPG to compress all messages prior to encryption by default?

By default, GPG compresses text during encryption. Additionally, RFC 4880 says: 2.3. Compression OpenPGP implementations SHOULD compress the message after applying the signature but before ...
8
votes
2answers
947 views

Zlib DEFLATE decompression bomb

Can you give me an example of a short data string that, when decompressed using Zlib's DEFLATE method, expands to something much much longer? More precisely: what is the nastiest decompression bomb ...
6
votes
1answer
1k views

Whats the best custom compression method to use when I have SSL?

Suppose I have an application which does encryption using SSL and provided you cannot control what cipher suite is being negotiated, and assuming that I have some custom compression over the data ...
6
votes
3answers
672 views

Encrypted password inside compressed archive

File compression utilities like Winrar or ZIP or 7zip encrypt the password and store it inside the archive. How safe is that? I mean you are giving away the archive with the password inside,it's not ...
6
votes
5answers
3k views

Does a binary executable have to have some critical plain-text components?

When companies package binary executables, they are often encrypted, compressed, scrambled, and otherwise made so that your lazy hacker can't simply open the program up in Notepad++ and see the code. ...
4
votes
3answers
383 views

Is gzipping content via TLS allowed?

So I have these few compression directives at http level in nginx: gzip on; gzip_http_version 1.1; gzip_vary on; I read that this should be avoided because of CRIME/BREACH attack, is this correct?
3
votes
1answer
585 views

Can Exchange/OWA still compress static images and be immune to HTTP compression attacks?

Microsoft Exchange / OWA (Outlook Web Access) allows for three different types of compression (link for Ex2010) Compression setting Description High Compresses both static and ...
3
votes
3answers
89 views

is g-zipping assets a security concern?

I recently noticed that the assets sent to clients aren't gzipped or minified on either my companies intranet or its public facing website. I brought this to the attention of the networking ...
3
votes
1answer
793 views

Does encrypting a file make it larger?

I encrypted a Word document using Winrar by setting a password. Surprisingly the archive was larger than the original file (631 vs 614KB). I then tested to see what would happen if encryption wasn't ...
3
votes
1answer
4k views

Detect a server supporting SPDY?

With my current interest in the CRIME attack, I am currently trying to check if there actually exits a way to "fingerprint" a server that supports SPDY? My research lead me to believe only that the ...
3
votes
2answers
148 views

Could HTTPS-Attacks like CRIME be mitigated by changing the session cookie regularly?

I was just reading about CRIME which is an attack to steal sensitive information by creating requests. Could this attack be mitigated, if the Server wouldn't send the client the actual session key to ...
3
votes
1answer
2k views

Do the BEAST and CRIME attacks apply to an IMAP service?

While setting up the Dovecot IMAP service, I noticed that the default parameters are not optimal, it allows SSLv3 for example. Using Thomas Pournin's TestSSLServer.java program, I saw the following: ....
3
votes
1answer
310 views

Is NTFS file compression vulnerable to a CRIME-like attack when using an encrypted volume?

I know that content compression can cause SSL to be vulnerable to the CRIME attack, via changes in the content length when injected plaintext matches existing content. Does this principle carry over ...
3
votes
1answer
1k views

With BREACH attack, is session-based CSRF token still secure?

This is something I haven't been able wrap my head around, if BREACH allow leaking of information, do we have to mask or generate CSRF token in a time-based or per-request fashion to make it more ...
2
votes
4answers
244 views

Which is more effective and 'secure': Compression+Encryption, or only Encryption?

This came up in an IRC discussion on freenode, and now I"m curious. The idea is that someone wants to determine whether or not encryption alone, or compression+encryption (with gpg/pgp being the ...
2
votes
3answers
139 views

Security of decompression tools

How safe is it to decompress untrusted files with unrar-free? With unzip? I'm using debian jessie. What steps can be taken to minimize the threat while extracting the file's contents?
2
votes
1answer
186 views

can you update a one-time pad, over one-time pad encryption (compressed)?

This might well be a silly question, but at the moment I've not thought of a reason it doesn't work. As I think is generally known, you should never re-use a one-time pad. But compression allows you ...
2
votes
2answers
113 views

Determine if compressed or encrypted [closed]

I have a bunch of network data and I would like to determine if it is either 1) encrypted or 2) compressed. I doubt it is both, but the potential exists. If I am assuming that the traditional ...
2
votes
1answer
96 views

Does storing your files as single compressed archives compromise integrity?

Compressing your files as tar.gz or zip for storage or backup saves space and is faster than handling thousands of files. But it looks like small corruptions in the archive, for example because of ...
2
votes
1answer
98 views

Security risks of symmetric encryption with compression for database data

I would like to compress data before encrypting and storing it in a MySQL database to reduce especially bandwith requirements. In the future, the DB may be accessible via a web interface. Various ...
2
votes
1answer
188 views

Would it be possible to add additional files to a password protected zip 2.0 file

I don't have the ability to determine/recover the master password for a production system that uses zip 2 archives. However, I need to be able to add new files to existing encrypted archives. There ...
1
vote
1answer
122 views

Decryping a RAR file with same password

I came across a problem very similar recently and wondered if anyone knew how to solve this. So say for example I have an RAR archive called archiveA.rar and a password to protect it the password is ...
1
vote
3answers
137 views

CRIME attack - If Javascript can be injected on the attacked machine, why not directly sending the cookie to a remove server?

I read about the CRIME - How to beat the BEAST successor? question and answer, but I don't understand that: If Javascript can be injected and run on the attacked machine, why not directly sending the ...
1
vote
2answers
187 views

How can I encrypt compressed data safely?

As mentioned in this particular answer, compressing data before encryption may lead to the CRIME attack, especially if the hacker has collected many similar versions of the transmitted data. Let's ...
1
vote
2answers
34 views

Can BREACH be thwarted by simply adding a sort of “salt” into the page being compressed?

Django supplies GZip middleware, but the docs issue a stark warning about BREACH, which I had, hitherto, forgotten about. The first thought I had was that I should be able modify the middleware to ...
1
vote
2answers
483 views

How to defeat CRIME, BREACH, TIME etc… server side (without sacrificing compression)

I am writing full-stack server side software and I have been researching CRIME attacks and it's relation to SPDY header compression as I am implementing the server side codecs for it at the moment. ...
0
votes
1answer
165 views

Can any ECC field element be safely serialized as “compressed” and then restored as uncompressed?

I have a library that stores all its ECC Field Elements in uncompressed form, in a bloated Base64 XML format, and storage has become a concern. (We want to support QR code as a form factor,etc) ...
0
votes
1answer
240 views

Disk level encryption + compression performance?

What are pros and cons for using disk level encryption like VeraCrypt and then turning on compression on mounted (virtually decrypted) drive? It seams to me that this can even increase some ...
0
votes
1answer
229 views

Can I test/determine all decryption types on an unkown filetype. I do have the password [closed]

I have a file that's nearly 200Mb. It was reportedly packed/encrypted with Kruptos 2. But it has a .~enc extension. The header of the file is pure gibberish. Running file says it's data running ...
0
votes
0answers
48 views

Can someone explain “two tries” in the CRIME attack on TLS

Ok, so I understand most of the attack, but when it comes to DEFLATE I'm not sure how two tries helps us get over the constraint that we see bytes where DEFLATE outputs bits. So basically, lets say ...
-1
votes
1answer
3k views

Is Opera spying on its users when traffic conpression is enabled?

Correct me if I misunderstand the following quoted paragraphs, but basically to compress something it must be decrypted first. This seems to be the claim of the article but I don't see this as true. ...
-2
votes
2answers
401 views

Can an compressed virus still do any harm to an OS [closed]

Let's say you have a piece of malware either as a standalone binary or hidden within a crafted image (two distinct cases). If I compress the standalone binary, can its mere presence as a compressed ...