We are often asked by the users whether our solutions support password recovery for PDF files on GPU’s from AMD or NVIDIA.
They do in certain cases. Please see more details below.
As certain algorithms are multithreaded not all of them can be successfully scaled up using a GPU. A couple of different reasons come to mind – in some cases it’s the general restriction of an algorithm, in other cases the complexity and expediency of such implementation.
When it comes to Adobe PDF and different versions of the format it has to be noted that the possibility of GPU-enabled password recovery has been influenced by all of the above-mentioned factors.
That is an obsolete file format with weak protection. The number of such files still in use is vanishingly small.
The format employs a short encryption key with the length of only 40 bits. With modern processing technologies and computing power you can unlock such PDF documents without knowing the password. All you need is to find the encryption key and decrypt the file.
Our online service AccessBack.com uses Passcovery rainbow tables to decrypt this kind of files with a 100% guarantee.
GPU-accelerated computing for Adobe PDF 1.1-1.3 [in our products] is not supported.
That’s another old and rare PDF format. There are not many files created in this format.
Protection of this file format is based on quite a long encryption key (128 bits) along with RC4-128 stream cipher, and later with block cipher (AES-128) algorithms. However despite various encryption techniques used in different versions of the format the password validation process has always remained the same and allowed for GPU-acceleration.
Recovery of passwords for this kind of PDF files on AMD/NVIDIA is fully implemented in our Passcovery Suite.
This one is the current version of PDF format. Though its index has not changed in a while but the Extension Level (EL3, EL5, EL7) and level of protection are steadily growing.
Password protection level in this version of PDF format proves that Adobe have taken a lot of effort with a great deal of creativity and efficiency. What makes the use of multithreading extremely difficult is that at the stage of key derivation, depending on the intermediate results when the key is stretched, SHA-2 hashing algorithms are used with keys of different lengths along with AES hashing.
Yes, starting from Adobe Acrobat 9 AES algorithm is used for hashing rather than encrypting. And that is quite an original and strong solution. It is very similar to Whirpool hashing algorithm used to generate keys in TrueCrypt.
Unpredictable key generation alone makes GPU-based implementation a no ordinary task that incurs a lot of nuances and additional processing of sharable data.
But the cherry on top is the use of AES as a hashing function at the stage of key derivation.
AES algorithm itself is difficult to implement on graphics cards and its use is even more doubtful due to speed parameters and availability of AES-NI in modern CPU’s. Processors with AES-enabled hardware show excellent results when recovering passwords for modern PDF files. While with GPU you will not get a significant acceleration.
Therefore [in our products] GPU-based password recovery of Adobe PDF 1.7 files is not supported.
The program is designed to quickly recover passwords to Adobe PDF documents of all versions.
AccentPPR instantly removes “Permissions password” (Master password). It searches for “Document open password” (User password) at the maximum speed of your computer. The source code of the program is specially optimized for this purpose.
To reduce searching time the program offers range customization option while featuring extended mask and dictionary attack with mutations control.
There are two versions of the program: for Windows x86/Windows x64.
The top Passcovery’s password recovery solution supporting a wide range of formats.
The program offers excellent options to customize the range of verification. Passcovery Suite also supports acceleration on AMD/NVIDIA graphics cards.
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