I Phil Gold have altered them to be more amenable to programming in Scala. Feedback is appreciatedparticularly on anything marked TODO.
Having a Glossary meant I could reduce the text on most pages, while expanding background for the definitions, and relating the ideas to other similar, contradictory, or more basic ideas. Why Bother with Definitions?
The value of a definition is insight. Simple descriptions are not always possible. Terms have meaning within particular contexts. Tedious examples may be required to expose the full meaning. Good definitions can expose assumptions and provide a basis for reasoning to larger conclusions.
Consider the idea that cryptography is used to keep secrets: We expect a cipher to win each and every contest brought by anyone who wishes to expose secrets. We call those people opponentsbut who are they really, and what can they do?
In practice, we cannot know. Opponents operate in secret: We do not know their names, nor how many they are, nor where they work. We do not know what they know, nor their level of experience or resources, nor anything else about them.
Because we do not know our opponents, we also do not know what they can do, including whether they can break our ciphers. Unless we know these things that cannot be known, we cannot tell whether a particular cipher design will prevail in battle. We cannot expect to know when our cipher has failed.
Even though the entire reason for using cryptography is to protect secret information, it is by definition impossible to know whether a cipher can do that. Nobody can know whether a cipher is strong enough, no matter how well educated they are, or how experienced, or how well connected, because they would have to know the opponents best of all.
The definition of cryptography implies a contest between a cipher design and unknown opponents, and that means a successful outcome cannot be guaranteed by anyone. Sometimes the Significance is Implied Consider the cryptographer who says: First, the cryptographer has the great disadvantage of not being able to prove cipher strength, nor to even list every possible attack so they can be checked.
In contrast, the cryptanalyst might be able to actually demonstrate weakness, but only by dint of massive effort which may not succeed, and will not be compensated even if it does.
Consequently, most criticisms will be extrapolations, possibly based on experience, and also possibly wrong. The situation is inherently unbalanced, with a bias against the cryptographer's detailed and thought-out claims, and for mere handwave first-thoughts from anyone who deigns to comment.
This is the ultimate conservative bias against anything new, and for the status quo.
Supposedly the bias exists because if the cryptographer's claim is wrong user secrets might be exposed. But the old status-quo ciphers are in that same position. Nothing about an old cipher makes it necessarily strong. Unfortunately, for users to benefit from cryptography they have to accept some strength argument.
Many years of trusted use do not testify about strength, but do provide both motive and time for opponents to develop secret attacks. Many failures to break a cipher do not imply it is strong.
There can be no expertise on the strength of unbroken ciphers. So on the one hand we need a cipher, and on the other have no way to know how strong the various ciphers are. For an industry, this is breathtakingly disturbing.
In modern society we purchase things to help us in some way. We go to the store, buy things, and they work. Or we notice the things do not work, and take them back.
We know to take things back because we can see the results.KEY STAGE 3 MATHEMATICS Exam Checklist Summer CAMBRIDGE HOUSE GRAMMAR SCHOOL PAGE 1 Year 9 1.
Number: Calculations and Rounding - Use BODMAS in calculations. Exponentiation is a mathematical operation, written as b n, involving two numbers, the base b and the exponent initiativeblog.com n is a positive integer, exponentiation corresponds to repeated multiplication of the base: that is, b n is the product of multiplying n bases: = × ⋯ × ⏟.
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Arithmetic sequence calculator The following arithmetic sequence calculator will help you determine the nth term and the sum of the first n terms of an arithmetic sequence. Given an arithmetic sequence with the first term a 1 and the common difference d, the n th (or general) term is given by a n = a 1 + (n − 1) d.
Example 1: Find the 27 th term of the arithmetic sequence 5, 8, 11, What is Bash? Bash is the shell, or command language interpreter, for the GNU operating system. The name is an acronym for the ‘Bourne-Again SHell’, a pun on Stephen Bourne, the author of the direct ancestor of the current Unix shell sh, which appeared in the Seventh Edition Bell Labs Research version of Unix.
Bash is largely compatible with sh and incorporates useful features from the.