Monthly Archives: November 2010

How many numbers don’t contain the digit 9?

Let’s see how many numbers from  to don’t contain the digit . For this kind of problem a computer scientist will most probably try to implement a sophisticated algorithm, a mathematician will try to find a direct formula, and a physicist will give … Continue reading

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Crypting files in c#

c# provides an easy to use API for encryption using symmetric key. The System.Security.Cryptography.RijndaelManaged class is an implementation for AES algorithm that supports key lengths of 128, 192, or 256 bits. An other very useful API is System.Security.Cryptography.CryptoStream that makes possible to crypt/decrypt data … Continue reading

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