vb.net barcode scanner webcam Figure 2-11 When the last block of plaintext ends in blank bytes, use padding to bring it up to size in Software

Printing Code 3/9 in Software Figure 2-11 When the last block of plaintext ends in blank bytes, use padding to bring it up to size

2
Code 39 Full ASCII Decoder In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
Encode Code39 In None
Using Barcode creation for Software Control to generate, create Code 3/9 image in Software applications.
data; this byte, a number from 1 to 16, indicates how many pad bytes have been added. In this example, after decrypting, we would know that the last 13 bytes of data should be discarded (see Figure 2-11). (Each of the last 13 bytes should be the number 13, so as an extra check, we make sure that each of them is 13.) If the length of the plaintext had been a multiple of 16, there would have been no need to pad. Nevertheless, it makes sense to always pad your data. Then, when decrypting, you know that the last byte decrypted is indeed a pad byte. To do that, you tack on 16 bytes, each of them the number 16.
Recognize Code 39 Extended In None
Using Barcode scanner for Software Control to read, scan read, scan image in Software applications.
Drawing ANSI/AIM Code 39 In Visual C#.NET
Using Barcode generator for .NET framework Control to generate, create Code 3 of 9 image in Visual Studio .NET applications.
Figure 2-11 When the last block of plaintext ends in blank bytes, use padding to bring it up to size
Code 39 Creator In VS .NET
Using Barcode encoder for ASP.NET Control to generate, create Code-39 image in ASP.NET applications.
Painting Code 3 Of 9 In VS .NET
Using Barcode encoder for .NET Control to generate, create Code 3 of 9 image in .NET applications.
Remember the known-plaintext attack If an algorithm is susceptible, that doesn t mean an attacker will automatically be able to break a message; it s necessary to find a plaintext/ciphertext pair first. The last block of data might be that known plaintext, because it contains padding. Of course, it s easy to simply use an algorithm that is not susceptible to the known-plaintext attack. One problem with block ciphers is that if the same block of plaintext appears in two places, it encrypts to the same ciphertext. In our printing machinery company memo, for example, the phrase slow third quarter may show up a number of times. Each time the first 16 bytes of that phrase is encrypted, it will produce the same ciphertext, and an attacker might identify this repeated pattern. To avoid having these kinds of copies in the ciphertext, you can use feedback modes. A number of these modes are discussed in the FAQ contained in the accompanying CD. The most common feedback mode is cipher block chaining (CBC), shown in Figure 2-12. In this scheme, you XOR the current block of plaintext with the preceding block of ciphertext (see Technical Note: XOR later in this chapter). For the first block of plaintext, there is no preceding block of ciphertext, so you XOR with an initialization vector (IV). When you decrypt the data, you copy a block of ciphertext, decrypt it, and XOR
Code 3/9 Generation In VB.NET
Using Barcode generator for Visual Studio .NET Control to generate, create Code 39 image in .NET framework applications.
Data Matrix 2d Barcode Drawer In None
Using Barcode generator for Software Control to generate, create DataMatrix image in Software applications.
Symmetric-Key Cryptography
Create Barcode In None
Using Barcode generation for Software Control to generate, create barcode image in Software applications.
Bar Code Printer In None
Using Barcode generation for Software Control to generate, create barcode image in Software applications.
Figure 2-12 Cipher block chaining. The first block of plaintext is XOR d with the IV and then encrypted. Each successive block is XOR d with the preceding block of ciphertext
Generate Code-128 In None
Using Barcode generator for Software Control to generate, create Code128 image in Software applications.
Code 3/9 Maker In None
Using Barcode drawer for Software Control to generate, create Code-39 image in Software applications.
the result with the preceding block of ciphertext (which you saved right before you decrypted it). This technique ensures that any duplicate block in the plaintext does not encrypt to the same ciphertext. That s all it does. It adds no other security. The encryption algorithm provides the security.
Leitcode Creator In None
Using Barcode generation for Software Control to generate, create Leitcode image in Software applications.
Print USS Code 128 In Java
Using Barcode printer for Java Control to generate, create Code-128 image in Java applications.
Stream Ciphers
Create Bar Code In Visual Basic .NET
Using Barcode printer for Visual Studio .NET Control to generate, create bar code image in .NET applications.
Data Matrix Reader In Visual C#.NET
Using Barcode recognizer for .NET Control to read, scan read, scan image in .NET framework applications.
To understand stream ciphers, the second type of symmetric-key algorithm, you need to first understand the cryptographic technique called a one-time pad, which is popular with spies. In one variation of this technique, you generate a bunch of random numbers, each from 0 to 25. Then you print two copies of the series. That s the pad. One copy stays at your headquarters, and the spy takes the other copy out into the field. To send a message back home, the spy encrypts each letter of the message with a number on the pad. The first letter of the message is encrypted with the first number on the pad, the second letter with the second number, and so on. Encryption is simply a matter of adding a numeric value assigned to the letter plus the number. Here s how the numeric value is assigned. If the plaintext letter is G and the number on the pad is 11, the ciphertext letter is R (R is the eleventh letter after G, or G 11 R). If the plaintext letter is Y and the number is 4, the ciphertext letter is C, or Y 4 (Y, Z, A, B, C; when you reach the end of the alphabet, you start over at A).
Bar Code Printer In Java
Using Barcode generation for Eclipse BIRT Control to generate, create barcode image in BIRT applications.
GS1 DataBar Expanded Generation In .NET
Using Barcode generation for .NET Control to generate, create GS1 DataBar Expanded image in Visual Studio .NET applications.
Create Linear In Java
Using Barcode printer for Java Control to generate, create Linear image in Java applications.
Bar Code Maker In Objective-C
Using Barcode drawer for iPhone Control to generate, create barcode image in iPhone applications.
Copyright © OnBarcode.com . All rights reserved.