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BlueCat is a Linux-based operating system for 64-bits processors.

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How to manage groups, users and permissions?

Linux is a multiuser and multitasking operating system, ie, multiple users can work on the system simultaneously running several tasks at once. It is therefore, very important that the operating system allows the management and control of users. Unix based systems organize all this by users and groups, where each user must be identified with a user name and password. During login, the password entered by each user, is encrypted and compared to the encrypted passwords that were previously stored in the system.
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Attack on AES: Omission of MixColumns

As we mentioned in a previous article, rounds that make up the AES algorithm can be divided into three different categories: initial rounds, standard round and final round. When encryption, the information is subjected to a different number of rounds (10, 12 and 14 respectively) in each case depending on the length of the key (128, 192 and 256 respectively). Each such round is made up of combinations of transformations, the possible transformations include: ByteSub, ShiftRow, MixColumns and AddRoundKey. Figure # 1 shows the relationship of the transformation and corresponding rounds.   Figure # 1: Distribution of the transformations in…
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How to obtain a traffic model for VoIP?

In order to perform estimations of a traffic model for multimedia flows, it is necessary for the researcher to have precise control of the test environment, minimizing errors and interference that may occur, leaving a test scenario that allows a smooth development to the application to be modeled. As an example, we have selected a VoIP traffic which is quite easy to interpret and it provides some of the things that must be done.   Scenario for testing Figure # 1 shows the diagram used for testing in order to obtain the pattern of traffic on the transmission of voice…
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What is VoIP?

The development of VoIP (Voice over Internet Protocol) technologies have been widely accepted by companies seeking lower costs for voice communications mainly in SMEs (Small and Medium Enterprises) environments. The term VoIP should not be confused with ToIP (Telephony over IP), VoIP refers to the technology required for voice communication over IP, while ToIP is a telephone service for users, which uses VoIP technology to give such service. VoIP allows voice transmission via an IP network, including those connected to the Internet. It involves digitizing voice signals, via a codec. The bandwidth consumption of such communication is directly related to…
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Cryptographic attack on AES: Impossible Differential Attack

Some time ago, I read an interesting article of a "successful attack" against AES, the famous symmetric-key algorithm. Raphael C.-W. Phan [1] presented a seven rounds "impossible differential attack" for AES-192 and AES-256. Someone may ask: what kind of attack is this?, well, it is a crypt-analysis that takes advantage of the differences that are impossible to be, in a data block through encryption, in order to discover the key?. Without going into many details of the method used, below I comment some of the most important results of this study. The attack involves taking pairs of identical texts in…
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