Introduction in .NET Assign code 128 barcode in .NET Introduction

Introduction using vs .net toproduce barcode 128 for web,windows application Java Platform and so is Visual Studio .NET code 128 barcode valid. On the other hand 0-987-65432-1 produces a check sum of 0 18 24 28 30 30 28 24 18 10 210 19 11 1 and so must contain at least one error.

The ISBN code can detect a single error but it cannot correct it and if there are two or more errors it may indicate that the ISBN is correct, when it isn t. The subject of error correcting and detecting codes requires some advanced mathematics and will not be considered further in this book. Interested readers should consult books such as [1.

1], [1.2], [1.3].

. Other methods of concealing messages There are Code-128 for .NET other methods for concealing the meaning or contents of a message that do not rely on codes or ciphers. The rst two are not relevant here but they deserve to be mentioned.

Such methods are. (1) the us e of secret or invisible ink, (2) the use of microdots, tiny photographs of the message on micro lm, stuck onto the message in a non-obvious place, (3) embedding the message inside an otherwise innocuous message, the words or letters of the secret message being scattered, according to some rule, throughout the non-secret message.. The rst t .NET Code 128A wo of these have been used by spies; the outstandingly successful double agent Juan Pujol, known as garbo, used both methods from 1942 to 1945 [1.5].

The third method has also been used by spies but may well also have been used by prisoners of war in letters home to pass on information as to where they were or about conditions in the camp; censors would be on the look-out for such attempts. The third method is discussed in 7. The examples throughout this book are almost entirely based upon English texts using either the 26-letter alphabet or an extended version of it to allow inclusion of punctuation symbols such as space, full stop and comma.

Modi cation of the examples to include more symbols or numbers or to languages with different alphabets presents no dif culties in theory. If, however, the cipher system is being implemented on a physical device it may be impossible to change the alphabet size without redesigning it; this is true of the Enigma and Hagelin machines, as we shall see later. Non-alphabetic languages, such as Japanese, would need to be alphabetised or, perhaps, treated as non-textual material as are photographs, maps, diagrams etc.

which can be enciphered by using specially. chapter 1 designed s .net framework Code 128C ystems of the type used in enciphering satellite television programmes or data from space vehicles..

Modular arithmetic In cryptog code 128 barcode for .NET raphy and cryptanalysis it is frequently necessary to add two streams of numbers together or to subtract one stream from the other but the form of addition or subtraction used is usually not that of ordinary arithmetic but of what is known as modular arithmetic. In modular arithmetic all additions and subtractions (and multiplications too, which we shall require in s 12 and 13) are carried out with respect to a xed number, known as the modulus.

Typical values of the modulus in cryptography are 2, 10 and 26. Whichever modulus is being used all the numbers which occur are replaced by their remainders when they are divided by the modulus. If the remainder is negative the modulus is added so that the remainder becomes non-negative.

If, for example, the modulus is 26 the only numbers that can occur are 0 to 25. If then we add 17 to 19 the result is 10 since 17 19 36 and 36 leaves remainder 10 when divided by 26. To denote that modulus 26 is being used we would write 17 19 10 (mod 26).

If we subtract 19 from 17 the result ( 2) is negative so we add 26, giving 24 as the result. The symbol is read as is congruent to and so we would say 36 is congruent to 10 (mod 26) and 2 is congruent to 24 (mod 26) . When two streams of numbers (mod 26) are added the rules apply to each pair of numbers separately, with no carry to the next pair.

Likewise when we subtract one stream from another (mod 26) the rules apply to each pair of digits separately with no borrowing from the next pair. Example 1.1 Add the stream 15 11 23 06 11 to the stream 17 04 14 19 23 (mod 26).

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