Python骇客密码如题，英文版，有兴趣的人可以看看。应用水平就看个人的天赋了 TABLE OF

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详细说明：如题，英文版，有兴趣的人可以看看。应用水平就看个人的天赋了 TABLE OF CONTENTS About This Book ....................................................................................................................... 6 Table of Contents ..................................................................................................................... 7 Chapter 1 - Making Paper Cryptography Tools ...................................................................... 1 What is Cryptography? ....................................................................... ......................................................................... 2 Codes vs. Ciphers ........................................................................................................................................................ 3 Making a Paper Cipher Wheel ..................................................................................................................................... 4 A Virtual Cipher Wheel ............................................................................................................................................... 7 How to Encrypt with the Cipher Wheel ....................................................................................................................... 8 How to Decrypt with the Cipher Wheel ....................................................................................................................... 9 A Different Cipher Tool: The St. Cyr Slide ............................................................................................................... 10 Practice Exercises, Chapter 1, Set A .......................................................................................................................... 11 Doing Cryptography without Paper Tools ................................................................................................................. 11 Practice Exercises, Chapter 1, Set B .......................................................................................................................... 13 Double-Strength Encryption?..................................................................................................................................... 13 Programming a Computer to do Encryption .............................................................................................................. 14 Chapter 2 - Installing Python.................................................................................................16 Downloading and Installing Python........................................................................................................................... 17 Downloading pyperclip.py......................................................................................................................................... 18 Starting IDLE............................................................................................................................................................. 18 The Featured Programs .............................................................................................................................................. 19 Line Numbers and Spaces.......................................................................................................................................... 20 Text Wrapping in This Book ..................................................................................................................................... 20 Tracing the Program Online....................................................................................................................................... 21 Checking Your Typed Code with the Online Diff Tool............................................................................................. 21 Copying and Pasting Text .......................................................................................................................................... 21 More Info Links ......................................................................................................................................................... 22 Programming and Cryptography................................................................................................................................ 22 Chapter 3 - The Interactive Shell..........................................................................................26 Some Simple Math Stuff............................................................................................................................................ 26 Integers and Floating Point Values ............................................................................................................................ 27 Expressions ................................................................................................................................................................ 27 Order of Operations ................................................................................................................................................... 28 Evaluating Expressions.............................................................................................................................................. 29 Errors are Okay!......................................................................................................................................................... 29 Practice Exercises, Chapter 3, Set A .......................................................................................................................... 30 Every Value has a Data Type..................................................................................................................................... 30 Storing Values in Variables with Assignment Statements ......................................................................................... 30 Overwriting Variables................................................................................................................................................ 32 Using More Than One Variable................................................................................................................................. 33 Variable Names.......................................................................................................................................................... 34 Practice Exercises, Chapter 3, Set B .......................................................................................................................... 35 Summary - But When Are We Going to Start Hacking?............................................................................................ 35 Chapter 4 - Strings and Writing Programs...........................................................................36 Strings........................................................................................................................................................................ 36 String Concatenation with the + Operator ................................................................................................................. 38 String Replication with the * Operator ...................................................................................................................... 39 Printing Values with the print() Function ............................................................................................................ 39 Escape Characters ...................................................................................................................................................... 40 Quotes and Double Quotes ........................................................................................................................................ 41 Practice Exercises, Chapter 4, Set A .......................................................................................................................... 42 Indexing ..................................................................................................................................................................... 42 Negative Indexes........................................................................................................................................................ 44 Slicing........................................................................................................................................................................ 44 Blank Slice Indexes.................................................................................................................................................... 45 Practice Exercises, Chapter 4, Set B .......................................................................................................................... 46 Writing Programs in IDLE’s File Editor.................................................................................................................... 46 Hello World!.............................................................................................................................................................. 47 Source Code of Hello World...................................................................................................................................... 47 Saving Your Program ................................................................................................................................................ 48 Running Your Program.............................................................................................................................................. 49 Opening The Programs You’ve Saved....................................................................................................................... 50 How the “Hello World” Program Works ................................................................................................................... 50 Comments .................................................................................................................................................................. 50 Functions.................................................................................................................................................................... 51 The print() function ............................................................................................................................................. 51 The input() function ............................................................................................................................................. 51 Ending the Program ................................................................................................................................................... 52 Practice Exercises, Chapter 4, Set C .......................................................................................................................... 52 Summary.................................................................................................................................................................... 53 Chapter 5 - The Reverse Cipher............................................................................................54 The Reverse Cipher.................................................................................................................................................... 54 Source Code of the Reverse Cipher Program............................................................................................................. 55 Sample Run of the Reverse Cipher Program.............................................................................................................. 55 Checking Your Source Code with the Online Diff Tool ............................................................................................ 56 How the Program Works............................................................................................................................................ 56 The len() Function ................................................................................................................................................. 57 Introducing the while Loop..................................................................................................................................... 58 The Boolean Data Type ............................................................................................................................................. 59 Comparison Operators ............................................................................................................................................... 59 Conditions.................................................................................................................................................................. 62 Blocks ........................................................................................................................................................................ 62 The while Loop Statement ...................................................................................................................................... 63 “Growing” a String .................................................................................................................................................... 64 Tracing Through the Program, Step by Step .............................................................................................................. 67 Using input() In Our Programs............................................................................................................................. 68 Practice Exercises, Chapter 5, Section A ................................................................................................................... 69 Summary.................................................................................................................................................................... 69 Chapter 6 - The Caesar Cipher..............................................................................................70 Implementing a Program............................................................................................................................................ 70 Source Code of the Caesar Cipher Program............................................................................................................... 71 Sample Run of the Caesar Cipher Program................................................................................................................ 72 Checking Your Source Code with the Online Diff Tool ............................................................................................ 73 Practice Exercises, Chapter 6, Set A .......................................................................................................................... 73 How the Program Works............................................................................................................................................ 73 Importing Modules with the import Statement....................................................................................................... 73 Constants.................................................................................................................................................................... 74 Theupper()andlower() StringMethods........................................................................................................75 The for Loop Statement........................................................................................................................................... 76 A while Loop Equivalent of a for Loop................................................................................................................ 77 Practice Exercises, Chapter 6, Set B .......................................................................................................................... 78 The if Statement ...................................................................................................................................................... 78 The else Statement.................................................................................................................................................. 79 The elif Statement.................................................................................................................................................. 79 Theinandnot inOperators.................................................................................................................................80 The find() String Method...................................................................................................................................... 81 Practice Exercises, Chapter 6, Set C .......................................................................................................................... 82 Back to the Code........................................................................................................................................................ 82 Displaying and Copying the Encrypted/Decrypted String ......................................................................................... 85 Encrypt Non-Letter Characters .................................................................................................................................. 86 Summary.................................................................................................................................................................... 87 Chapter 7 - Hacking the Caesar Cipher with the Brute-Force Technique..........................88 Hacking Ciphers ........................................................................................................................................................ 88 The Brute-Force Attack ............................................................................................................................................. 89 Source Code of the Caesar Cipher Hacker Program .................................................................................................. 89 Sample Run of the Caesar Cipher Hacker Program ................................................................................................... 90 How the Program Works............................................................................................................................................ 91 The range() Function ............................................................................................................................................ 91 Back to the Code........................................................................................................................................................ 93 String Formatting ....................................................................................................................................................... 94 Practice Exercises, Chapter 7, Set A .......................................................................................................................... 95 Summary.................................................................................................................................................................... 95 Chapter 8 - Encrypting with the Transposition Cipher ........................................................ 96 Encrypting with the Transposition Cipher ................................................................................................................. 96 Practice Exercises, Chapter 8, Set A .......................................................................................................................... 98 A Transposition Cipher Encryption Program............................................................................................................. 98 Source Code of the Transposition Cipher Encryption Program ................................................................................. 98 Sample Run of the Transposition Cipher Encryption Program .................................................................................. 99 How the Program Works.......................................................................................................................................... 100 Creating Your Own Functions with def Statements............................................................................................... 100 The Program’s main() Function ........................................................................................................................... 101 Parameters................................................................................................................................................................ 102 Variables in the Global and Local Scope ................................................................................................................. 104 The global Statement ........................................................................................................................................... 104 Practice Exercises, Chapter 8, Set B ........................................................................................................................ 106 The List Data Type .................................................................................................................................................. 106 Using the list() Function to Convert Range Objects to Lists ............................................................................. 109 Reassigning the Items in Lists.................................................................................................................................. 110 Reassigning Characters in Strings............................................................................................................................ 110 Lists of Lists ............................................................................................................................................................ 110 Practice Exercises, Chapter 8, Set C ........................................................................................................................ 111 Using len() and the in Operator with Lists ......................................................................................................... 111 List Concatenation and Replication with the + and * Operators.............................................................................. 112 Practice Exercises, Chapter 8, Set D ........................................................................................................................ 113 The Transposition Encryption Algorithm ................................................................................................................ 113 Augmented Assignment Operators .......................................................................................................................... 115 Back to the Code...................................................................................................................................................... 116 The join() String Method.................................................................................................................................... 118 Return Values and return Statements .................................................................................................................. 119 Practice Exercises, Chapter 8, Set E ........................................................................................................................ 120 Back to the Code...................................................................................................................................................... 120 The Special __name__ Variable............................................................................................................................ 120 Key Size and Message Length ................................................................................................................................. 121 Summary.................................................................................................................................................................. 122 Chapter 9 - Decrypting with the Transposition Cipher ......................................................123 Decrypting with the Transposition Cipher on Paper ................................................................................................ 124 Practice Exercises, Chapter 9, Set A ........................................................................................................................ 125 A Transposition Cipher Decryption Program........................................................................................................... 126 Source Code of the Transposition Cipher Decryption Program ............................................................................... 126 How the Program Works.......................................................................................................................................... 127 The math.ceil(), math.floor() and round() Functions......................................................................... 128 The and and or Boolean Operators........................................................................................................................ 132 Practice Exercises, Chapter 9, Set B ........................................................................................................................ 133 Truth Tables............................................................................................................................................................. 133 The and and or Operators are Shortcuts ................................................................................................................ 134 Order of Operations for Boolean Operators ............................................................................................................. 135 Back to the Code...................................................................................................................................................... 135 Practice Exercises, Chapter 9, Set C ........................................................................................................................ 137 Summary.................................................................................................................................................................. 137 Chapter 10 - Programming a Program to Test Our Program ............................................138 Source Code of the Transposition Cipher Tester Program....................................................................................... 139 Sample Run of the Transposition Cipher Tester Program........................................................................................ 140 How the Program Works.......................................................................................................................................... 141 Pseudorandom Numbers and the random.seed() Function............................................................................... 141 The random.randint() Function ..................................................................................................................... 143 References................................................................................................................................................................ 143 The copy.deepcopy() Functions...................................................................................................................... 147 Practice Exercises, Chapter 10, Set A ...................................................................................................................... 148 The random.shuffle() Function ..................................................................................................................... 148 Randomly Scrambling a String ................................................................................................................................ 149 Back to the Code...................................................................................................................................................... 149 The sys.exit() Function ................................................................................................................................... 150 Testing Our Test Program........................................................................................................................................ 151 Summary.................................................................................................................................................................. 152 Chapter 11 - Encrypting and Decrypting Files...................................................................153 Plain Text Files ........................................................................................................................................................ 154 Source Code of the Transposition File Cipher Program........................................................................................... 154 Sample Run of the Transposition File Cipher Program ........................................................................................... 157 Reading From Files.................................................................................................................................................. 157 Writing To Files....................................................................................................................................................... 158 How the Program Works.......................................................................................................................................... 159 The os.path.exists() Function ..................................................................................................................... 160 The startswith() and endswith() String Methods..................................................................................... 161 The title() String Method ................................................................................................................................. 162 The time Module and time.time() Function .................................................................................................. 163 Back to the Code...................................................................................................................................................... 164 Practice Exercises, Chapter 11, Set A ...................................................................................................................... 165 Summary.................................................................................................................................................................. 165 Chapter 12 - Detecting English Programmatically............................................................166 How Can a Computer Understand English?............................................................................................................. 167 Practice Exercises, Chapter 12, Section A ............................................................................................................... 169 The Detect English Module ..................................................................................................................................... 169 Source Code for the Detect English Module............................................................................................................ 169 How the Program Works.......................................................................................................................................... 170 Dictionaries and the Dictionary Data Type .............................................................................................................. 171 Adding or Changing Items in a Dictionary .............................................................................................................. 172 Practice Exercises, Chapter 12, Set B ...................................................................................................................... 173 Using the len() Function with Dictionaries.......................................................................................................... 173 Using the in Operator with Dictionaries................................................................................................................. 173 Using for Loops with Dictionaries ........................................................................................................................ 174 Practice Exercises, Chapter 12, Set C ...................................................................................................................... 174 The Difference Between Dictionaries and Lists....................................................................................................... 174 Finding Items is Faster with Dictionaries Than Lists............................................................................................... 175 The split() Method ............................................................................................................................................ 175 The None Value ...................................................................................................................................................... 176 Back to the Code...................................................................................................................................................... 177 “Divide by Zero” Errors........................................................................................................................................... 179 The float(), int(), and str() Functions and Integer Division ..................................................................... 179 Practice Exercises, Chapter 12, Set D ...................................................................................................................... 180 Back to the Code...................................................................................................................................................... 180 The append() List Method..................................................................................................................................... 182 Default Arguments................................................................................................................................................... 183 Calculating Percentage............................................................................................................................................. 184 Practice Exercises, Chapter 12, Set E ...................................................................................................................... 185 Summary.................................................................................................................................................................. 186 Chapter 13 - Hacking the Transposition Cipher ................................................................187 Source Code of the Transposition Cipher Hacker Program ..................................................................................... 187 Sample Run of the Transposition Breaker Program ................................................................................................. 189 How the Program Works.......................................................................................................................................... 190 Multi-line Strings with Triple Quotes ...................................................................................................................... 190 Back to the Code...................................................................................................................................................... 191 The strip() String Method ................................................................................................................................. 193 Practice Exercises, Chapter 13, Set A ...................................................................................................................... 195 Summary.................................................................................................................................................................. 195 Chapter 14 - Modular Arithmetic with the Multiplicative and Affine Ciphers .................196 Oh No Math!............................................................................................................................................................ 197 Math Oh Yeah! ........................................................................................................................................................ 197 Modular Arithmetic (aka Clock Arithmetic)............................................................................................................ 197 The % Mod Operator ............................................................................................................................................... 199 Practice Exercises, Chapter 14, Set A ...................................................................................................................... 199 GCD: Greatest Common Divisor (aka Greatest Common Factor) ........................................................................... 199 Visualize Factors and GCD with Cuisenaire Rods................................................................................................... 200 Practice Exercises, Chapter 14, Set B ...................................................................................................................... 202 Multiple Assignment................................................................................................................................................ 202 Swapping Values with the Multiple Assignment Trick............................................................................................ 203 Euclid’s Algorithm for Finding the GCD of Two Numbers..................................................................................... 203 “Relatively Prime” ................................................................................................................................................... 205 Practice Exercises, Chapter 14, Set C ...................................................................................................................... 205 The Multiplicative Cipher........................................................................................................................................ 205 Practice Exercises, Chapter 14, Set D ...................................................................................................................... 207 Multiplicative Cipher + Caesar Cipher = The Affine Cipher ................................................................................... 207 The First Affine Key Problem.................................................................................................................................. 207 Decrypting with the Affine Cipher........................................................................................................................... 208 Finding Modular Inverses ........................................................................................................................................ 209 The // Integer Division Operator ........................................................................................................................... 210 Source Code of the cryptomath Module............................................................................................................. 210 Practice Exercises, Chapter 14, Set E ...................................................................................................................... 211 Summary.................................................................................................................................................................. 211 Chapter 15 - The Affine Cipher ...........................................................................................213 Source Code of the Affine Cipher Program ............................................................................................................. 214 Sample Run of the Affine Cipher Program .............................................................................................................. 216 Practice Exercises, Chapter 15, Set A ...................................................................................................................... 216 How the Program Works.......................................................................................................................................... 216 Splitting One Key into Two Keys ............................................................................................................................ 218 The Tuple Data Type ............................................................................................................................................... 218 Input Validation on the Keys ................................................................................................................................... 219 The Affine Cipher Encryption Function .................................................................................................................. 220 The Affine Cipher Decryption Function .................................................................................................................. 221 Generating Random Keys ........................................................................................................................................ 222 The Second Affine Key Problem: How Many Keys Can the Affine Cipher Have? ................................................. 223 Summary.................................................................................................................................................................. 225 Chapter 16 - Hacking the Affine Cipher.............................................................................226 Source Code of the Affine Cipher Hacker Program................................................................................................. 226 Sample Run of the Affine Cipher Hacker Program.................................................................................................. 228 How the Program Works.......................................................................................................................................... 228 The Affine Cipher Hacking Function....................................................................................................................... 230 The ** Exponent Operator ...................................................................................................................................... 230 The continue Statement ...................................................................................................................................... 231 Practice Exercises, Chapter 16, Set A ...................................................................................................................... 234 Summary.................................................................................................................................................................. 234 Chapter 17 - The Simple Substitution Cipher ....................................................................235 The Simple Substitution Cipher with Paper and Pencil ........................................................................................... 236 Practice Exercises, Chapter 17, Set A ...................................................................................................................... 236 Source Code of the Simple Substitution Cipher....................................................................................................... 237 Sample Run of the Simple Substitution Cipher Program ......................................................................................... 239 How the Program Works.......................................................................................................................................... 239 The Program’s main() Function ........................................................................................................................... 240 The sort() List Method ....................................................................................................................................... 241 Wrapper Functions................................................................................................................................................... 242 The Program’s translateMessage() Function............................................................................................... 243 The isupper() and islower() String Methods .............................................................................................. 245 Practice Exercises, Chapter 17, Set B ...................................................................................................................... 247 Generating a Random Key....................................................................................................................................... 247 Encrypting Spaces and Punctuation ......................................................................................................................... 248 Practice Exercises, Chapter 17, Set C ...................................................................................................................... 249 Summary.................................................................................................................................................................. 249 Chapter 18 - Hacking the Simple Substitution Cipher ......................................................250 Computing Word Patterns........................................................................................................................................ 251 Getting a List of Candidates for a Cipherword ........................................................................................................ 252 Practice Exercises, Chapter 18, Set A ...................................................................................................................... 253 Source Code of the Word Pattern Module ............................................................................................................... 253 Sample Run of the Word Pattern Module ................................................................................................................ 255 How the Program Works.......................................................................................................................................... 256 The pprint.pprint() and pprint.pformat() Functions ........................................................................ 256 Building Strings in Python with Lists ...................................................................................................................... 257 Calculating the Word Pattern ................................................................................................................................... 258 The Word Pattern Program’s main() Function ..................................................................................................... 259 Hacking the Simple Substitution Cipher .................................................................................................................. 262 Source Code of the Simple Substitution Hacking Program...................................................................................... 262 Hacking the Simple Substitution Cipher (in Theory) ............................................................................................... 266 Explore the Hacking Functions with the Interactive Shell ....................................................................................... 266 How the Program Works.......................................................................................................................................... 271 Import All the Things............................................................................................................................................... 272 A Brief Intro to Regular Expressions and the sub() Regex Method ......................................................................... 272 The Hacking Program’s main() Function............................................................................................................. 273 Partially Hacking the Cipher.................................................................................................................................... 274 Blank Cipherletter Mappings ................................................................................................................................... 275 Adding Letters to a Cipherletter Mapping ............................................................................................................... 276 Intersecting Two Letter Mappings ........................................................................................................................... 277 Removing Solved Letters from the Letter Mapping................................................................................................. 278 Hacking the Simple Substitution Cipher .................................................................................................................. 281 Creating a Key from a Letter Mapping .................................................................................................................... 283 Couldn’t We Just Encrypt the Spaces Too? ............................................................................................................. 285 Summary.................................................................................................................................................................. 286 Chapter 19 - The Vigenère Cipher ......................................................................................287 Le Chiffre Indéchiffrable ......................................................................................................................................... 288 Multiple “Keys” in the Vigenère Key ...................................................................................................................... 288 Source Code of Vigenère Cipher Program............................................................................................................... 291 Sample Run of the Vigenère Cipher Program.......................................................................................................... 294 How the Program Works.......................................................................................................................................... 294 Summary.................................................................................................................................................................. 298 Chapter 20 - Frequency Analysis........................................................................................299 The Code for Matching Letter Frequencies ............................................................................................................. 304 How the Program Works.......................................................................................................................................... 306 The Most Common Letters, “ETAOIN” .................................................................................................................. 307 The Program’s getLettersCount() Function ................................................................................................. 307 The Program’s getItemAtIndexZero() Function .......................................................................................... 308 The Program’s getFrequencyOrder() Function ............................................................................................ 308 The sort() Method’s key and reverse Keyword Arguments ......................................................................... 310 Passing Functions as Values .................................................................................................................................... 311 Converting Dictionaries to Lists with the keys(), values(), items() Dictionary Methods ......................................... 313 Sorting the Items from a Dictionary......................................................................................................................... 315 The Program’s englishFreqMatchScore() Function ................................................................................... 316 Summary.................................................................................................................................................................. 317 Chapter 21 - Hacking the Vigenère Cipher ........................................................................318 The Dictionary Attack.............................................................................................................................................. 319 Source Code for a Vigenère Dictionary Attack Program ......................................................................................... 319 Sample Run of the Vigenère Dictionary Hacker Program ....................................................................................... 320 The readlines() File Object Method ................................................................................................................ 321 The Babbage Attack & Kasiski Examination........................................................................................................... 321 Kasiski Examination, Step 1 – Find Repeat Sequences’ Spacings........................................................................... 321 Kasiski Examination, Step 2 – Get Factors of Spacings .......................................................................................... 322 Get Every Nth Letters from a String ........................................................................................................................ 323 Frequency Analysis.................................................................................................................................................. 323 Brute-Force through the Possible Keys.................................................................................................................... 325 Source Code for the Vigenère Hacking Program ..................................................................................................... 326 Sample Run of the Vigenère Hacking Program ....................................................................................................... 332 How the Program Works.......................................................................................................................................... 334 Finding Repeated Sequences ................................................................................................................................... 335 Calculating Factors .................................................................................................................................................. 337 Removing Duplicates with the set() Function .......................................................................................................... 338 The Kasiski Examination Algorithm........................................................................................................................ 341 The extend() List Method................................................................................................................................... 342 The end Keyword Argument for print() ........................................................................................................... 347 The itertools.product() Function.............................................................................................................. 348 The break Statement ............................................................................................................................................. 352 Practice Exercises, Chapter 21, Set A ...................................................................................................................... 354 Modifying the Constants of the Hacking Program................................................................................................... 354 Summary.................................................................................................................................................................. 355 Chapter 22 - The One-Time Pad Cipher ..............................................................................356 The Unbreakable One-Time Pad Cipher.................................................................................................................. 357 Why the One-Time Pad is Unbreakable................................................................................................................... 357 Beware Pseudorandomness...................................................................................................................................... 358 Beware the Two-Time Pad ...................................................................................................................................... 358 The Two-Time Pad is the Vigenère Cipher.............................................................................................................. 359 Practice Exercises, Chapter 22, Set A ...................................................................................................................... 360 Summary.................................................................................................................................................................. 360 Chapter 23 - Finding Prime Numbers.................................................................................361 Prime Numbers ........................................................................................................................................................ 362 Composite Numbers................................................................................................................................................. 363 Source Code for The Prime Sieve Module............................................................................................................... 363 How the Program Works.......................................................................................................................................... 364 How to Calculate if a Number is Prime ................................................................................................................... 365 The Sieve of Eratosthenes........................................................................................................................................ 366 The primeSieve() Function............................................................................................................................... 368 Detecting Prime Numbers ........................................................................................................................................ 369 Source Code for the Rabin-Miller Module............................................................................................................... 370 Sample Run of the Rabin Miller Module ................................................................................................................. 372 How the Program Works.......................................................................................................................................... 372 The Rabin-Miller Primality Algorithm .................................................................................................................... 372 The New and Improved isPrime() Function ...................................................................................................... 373 Summary.................................................................................................................................................................. 375 Chapter 24 - Public Key Cryptography and the RSA Cipher..............................................378 Public Key Cryptography......................................................................................................................................... 379 The Dangers of “Textbook” RSA ............................................................................................................................ 381 A Note About Authentication .................................................................................................................................. 381 The Man-In-The-Middle Attack .............................................................................................................................. 382 Generating Public and Private Keys......................................................................................................................... 383 Source Code for the RSA Key Generation Program ................................................................................................ 383 Sample Run of the RSA Key Generation Program .................................................................................................. 385 How the Key Generation Program Works ............................................................................................................... 386 The Program’s generateKey() Function........................................................................................................... 387 RSA Key File Format .............................................................................................................................................. 390 Hybrid Cryptosystems ............................................................................................................................................. 391 Source Code for the RSA Cipher Program .............................................................................................................. 391 Sample Run of the RSA Cipher Program................................................................................................................. 395 Practice Exercises, Chapter 24, Set A ...................................................................................................................... 397 Digital Signatures .................................................................................................................................................... 397 How the RSA Cipher Program Works ..................................................................................................................... 398 ASCII: Using Numbers to Represent Characters ..................................................................................................... 400 The chr() and ord() Functions .......................................................................................................................... 400 Practice Exercises, Chapter 24, Set B ...................................................................................................................... 401 Blocks ...................................................................................................................................................................... 401 Converting Strings to Blocks with getBlocksFromText() ............................................................................. 404 The encode() String Method and the Bytes Data Type ....................................................................................... 405 The bytes() Function and decode() Bytes Method ........................................................................................ 405 Practice Exe

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