In his favorite university I had to make an example of block and stream encryption. Well, I think now quickly .. but quickly failed. The encryption operations comprise exponentiation. For example, the character "A" is number 97 in the table ASCII. And according to an exponential encryption, it had to be raised to the third degree. But! PC works only with 20-digit numbers, but here turns 47-digit (later I found out). Ie personalka basically can not work with such numbers. What to do? And this is a separate issue from the area of \u200b\u200bprogramming and it is called "Long arithmetic." Do you know how much sitting? Almost a month. Rummaged sea sites on the subject, and even a special book bought Hummingbird .. As a result, I made it exponentiation - by multiplying a column! The algorithm allows to get the number of such length, three-screen (in pascal). The encryption algorithm did not have to do, but mentally figure out how to do it. Nervous get the situation but I learned a lot. You also suggest that a concentrated experience, all ready, (oh, I would be so ..) The program is written in Pascal, then moved to Delphi.
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