6 ms·

A JPEG that becomes a PNG after AES encryption and a PDF after 3DES decryption

240 points by soundsop 12y ago

tiles 12y ago
The raw file: * (JPG) https://corkami.googlecode.com/svn-history/r1906/trunk/src/angecryption/PoCs/mrmcd.jpg https://corkami.googlecode.com/svn-history/r1906/trunk/src/a...
nathancahill 12y ago
The file in question: https://corkami.googlecode.com/svn-history/r1906/trunk/src/angecryption/PoCs/mrmcd.jpg https://corkami.googlecode.com/svn-history/r1906/trunk/src/a... (direct download, 173kb) Imgur mirror: http://i.imgur.com/jUEAygp.jpg http://i.imgur.com/jUEAygp.jpg
- nwh 12y ago
  People are going to be mighty confused if they try to use that, imgur re-encodes all of it's images uploaded.
  - gpvos 12y ago
    Even JPEGs? That would explain some of the bad quality images on there. Or do they re-encode without recompressing, à la jpegtran?
    - iancarroll 12y ago
      They do compression on big images IIRC
  - josu 12y ago
    Yep, 45KB vs 143KB.
- eik3_de 12y ago
  Lol that's funny: I took my math classes exactly in that building. University of Applied Sciences, Darmstadt, Germany. www.h-da.de
diafygi 12y ago
Previous discussion: https://news.ycombinator.com/item?id=7775015 https://news.ycombinator.com/item?id=7775015
- deleted 12y ago
  [deleted]
pushedx 12y ago
Does anyone know what block size is needed, IV, cypher mode?
- shuzchen 12y ago
  The python file in that commit shows you everything you need: https://code.google.com/p/corkami/source/browse/trunk/src/angecryption/PoCs/mrmcd.py?spec=svn1906&r=1906 https://code.google.com/p/corkami/source/browse/trunk/src/an...
deleted 12y ago
[deleted]
gear54rus 12y ago
How in the hell does one discover that kind of thing? :) I don't really know much about crypto and symmetric ciphers in general, but aren't the odds of discovering something that converts from JPEG to PNG by applying AES extremely small? Let alone something that ALSO goes from JPEG to PDF by applying 3DES. I presume there is some algorithm based on the nature of ciphers themselves?
- andrewchambers 12y ago
  Only the file headers need to be valid, and generating a new file is as simple brute forcing encryption with random keys and then checking for a minimal correct file header.
- gizmo686 12y ago
  I didn't check this demo in particular, but I have seen this trick before. The first observation needed is that you can insert an arbitrary block of data into the picture without changing how it renders. The second observation is that AES is a symmetric algorithm, meaning decryption is the same operation as encryption. Using this, you can encrypt the PNG, and embed the result in the unencrypted JPEG. Then, when you encrypt the JPEG, you encrypt the embedded PNG. There are a couple of complications to this. The major one is that both formats require correct data near the begging of the file. The size of this region is small enough that it is feasible to brute force passwords until you find one that works.
  - nightcracker 12y ago
    AES encryption is not the same as decryption.
  - mehrdada 12y ago
    You get the definition of "symmetric" wrong. Symmetric encryption refers to using the same key for encryption and decryption, as opposed to asymmetric, aka public-key encryption. By no means AESEncrypt and AESDecrypt are the same functions. That said, some encryption modes employing AES, like AES in CTR mode, are based on generating a pseudo-random keystream and XORing it with cleartext to get the ciphertext. The inverse of that operation is itself, but that has nothing to do with the term "symmetric encryption". This particular case uses AES in CBC mode, which is not symmetric in that sense.
zrm 12y ago
See also The International Journal of Proof-of-Concept Or Get The Fuck Out. https://archive.org/details/Pocorgtfo00 https://archive.org/details/Pocorgtfo00 https://archive.org/details/Pocorgtfo01 https://archive.org/details/Pocorgtfo01 https://archive.org/details/Pocorgtfo02 https://archive.org/details/Pocorgtfo02 https://archive.org/details/pocorgtfo03 https://archive.org/details/pocorgtfo03 https://archive.org/details/pocorgtfo04 https://archive.org/details/pocorgtfo04 https://archive.org/details/pocorgtfo05 https://archive.org/details/pocorgtfo05
- voltagex_ 12y ago
  For the uninitiated, some of these files are bootable (on x86), or contain other goodies hidden somehow. These are written (or collated) by Travis Goodspeed - travisgoodspeed.blogspot.com
  - snake_plissken 12y ago
    This blog is amazing! Very motivating. Thanks for sharing.
dmead 12y ago
GOD WHERE IS THE PICTURE IM FREAKING OUT
sprkyco 12y ago
tl:dr I'm a fanboy of Corkami and just wanted to show appreciation. Ange Albertini does some amazing research and I was orginally introduced to his works after reading POC||GTFO from a Talk Travis Goodspeed gave. Recently Corkami did a giveaway on twitter for a signed mini-poster (Corkami's Posters are amazing as well highly recommended!) Fortunately I have a signed mini-poster en route to my mailbox cannot wait to have that thing framed.

240 points by soundsop 12y ago

tiles 12y ago

The raw file: * (JPG) https://corkami.googlecode.com/svn-history/r1906/trunk/src/angecryption/PoCs/mrmcd.jpg https://corkami.googlecode.com/svn-history/r1906/trunk/src/a...

nathancahill 12y ago

The file in question: https://corkami.googlecode.com/svn-history/r1906/trunk/src/angecryption/PoCs/mrmcd.jpg https://corkami.googlecode.com/svn-history/r1906/trunk/src/a... (direct download, 173kb) Imgur mirror: http://i.imgur.com/jUEAygp.jpg http://i.imgur.com/jUEAygp.jpg

nwh 12y ago
People are going to be mighty confused if they try to use that, imgur re-encodes all of it's images uploaded.
- gpvos 12y ago
  Even JPEGs? That would explain some of the bad quality images on there. Or do they re-encode without recompressing, à la jpegtran?
  - iancarroll 12y ago
    They do compression on big images IIRC
- josu 12y ago
  Yep, 45KB vs 143KB.
eik3_de 12y ago
Lol that's funny: I took my math classes exactly in that building. University of Applied Sciences, Darmstadt, Germany. www.h-da.de

diafygi 12y ago

Previous discussion: https://news.ycombinator.com/item?id=7775015 https://news.ycombinator.com/item?id=7775015

deleted 12y ago
[deleted]

pushedx 12y ago

Does anyone know what block size is needed, IV, cypher mode?

shuzchen 12y ago
The python file in that commit shows you everything you need: https://code.google.com/p/corkami/source/browse/trunk/src/angecryption/PoCs/mrmcd.py?spec=svn1906&r=1906 https://code.google.com/p/corkami/source/browse/trunk/src/an...

deleted 12y ago

[deleted]

gear54rus 12y ago

How in the hell does one discover that kind of thing? :) I don't really know much about crypto and symmetric ciphers in general, but aren't the odds of discovering something that converts from JPEG to PNG by applying AES extremely small? Let alone something that ALSO goes from JPEG to PDF by applying 3DES. I presume there is some algorithm based on the nature of ciphers themselves?

andrewchambers 12y ago
Only the file headers need to be valid, and generating a new file is as simple brute forcing encryption with random keys and then checking for a minimal correct file header.
gizmo686 12y ago
I didn't check this demo in particular, but I have seen this trick before. The first observation needed is that you can insert an arbitrary block of data into the picture without changing how it renders. The second observation is that AES is a symmetric algorithm, meaning decryption is the same operation as encryption. Using this, you can encrypt the PNG, and embed the result in the unencrypted JPEG. Then, when you encrypt the JPEG, you encrypt the embedded PNG. There are a couple of complications to this. The major one is that both formats require correct data near the begging of the file. The size of this region is small enough that it is feasible to brute force passwords until you find one that works.
- nightcracker 12y ago
  AES encryption is not the same as decryption.
- mehrdada 12y ago
  You get the definition of "symmetric" wrong. Symmetric encryption refers to using the same key for encryption and decryption, as opposed to asymmetric, aka public-key encryption. By no means AESEncrypt and AESDecrypt are the same functions. That said, some encryption modes employing AES, like AES in CTR mode, are based on generating a pseudo-random keystream and XORing it with cleartext to get the ciphertext. The inverse of that operation is itself, but that has nothing to do with the term "symmetric encryption". This particular case uses AES in CBC mode, which is not symmetric in that sense.

zrm 12y ago

See also The International Journal of Proof-of-Concept Or Get The Fuck Out. https://archive.org/details/Pocorgtfo00 https://archive.org/details/Pocorgtfo00 https://archive.org/details/Pocorgtfo01 https://archive.org/details/Pocorgtfo01 https://archive.org/details/Pocorgtfo02 https://archive.org/details/Pocorgtfo02 https://archive.org/details/pocorgtfo03 https://archive.org/details/pocorgtfo03 https://archive.org/details/pocorgtfo04 https://archive.org/details/pocorgtfo04 https://archive.org/details/pocorgtfo05 https://archive.org/details/pocorgtfo05

voltagex_ 12y ago
For the uninitiated, some of these files are bootable (on x86), or contain other goodies hidden somehow. These are written (or collated) by Travis Goodspeed - travisgoodspeed.blogspot.com
- snake_plissken 12y ago
  This blog is amazing! Very motivating. Thanks for sharing.

dmead 12y ago

GOD WHERE IS THE PICTURE IM FREAKING OUT

sprkyco 12y ago

tl:dr I'm a fanboy of Corkami and just wanted to show appreciation. Ange Albertini does some amazing research and I was orginally introduced to his works after reading POC||GTFO from a Talk Travis Goodspeed gave. Recently Corkami did a giveaway on twitter for a signed mini-poster (Corkami's Posters are amazing as well highly recommended!) Fortunately I have a signed mini-poster en route to my mailbox cannot wait to have that thing framed.