Posts tagged: 40-bit keys

MS Office 40-bit key searching on GPU

In one of the first notes in this blog I have already spoken about the encryption details used in different versions of Microsoft Office. Certainly it was interesting for me whether it is possible to apply technology of general-purpose computations on video cards (CUDA) to speed up the process of key recovery for MS Office. The most important bottleneck was the RC4 algorithm which is basic in almost all Office versions encryption. In the Internet I saw responses that RC4 implementation on CUDA was almost more slowly than on CPU which meant that RC4 algorithm did not fit for optimized GPU implementation. Read more »

Encryption evolution in Microsoft Office

In the conclusion of my article ‘On cryptosystems untrustworthiness’, written in 1998, I specified that the using the strong cryptography in application is gradually changing for the better. Lets consider evolution of cryptographic capabilities used by the one of the most popular applications for personal computers – MS Office, šespecially because recently Microsoft has officially opened specifications of this software, including encryption algorithms used. Here below I will speak only about passwords for file opening, because when using any other passwords (read-only access etc.) the text of the document is not encrypted and that is why they can be easily bypassed. Read more »

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