Python Cryptography Programming (2nd Edition)

Python Cryptography Programming (2nd Edition) is Al Sweigart's hands-on introduction to cryptography for beginning programmers; the Chinese edition is translated from the second edition of the original, whose English title is Cracking Codes with Python. Using Python as its tool, the book starts from a point that requires no programming background: it first has readers make paper cryptography tools and become familiar with the interactive environment and string operations, then step by step implements classical ciphers such as the reverse cipher, Caesar cipher, transposition cipher, affine cipher, simple substitution cipher, and Vigenère cipher. Each algorithm unfolds in three stages—principle, implementation, cracking: first the encryption idea is explained, then annotated Python code is given, and finally a program is written to break the ciphertext, with practical techniques such as brute-force enumeration, frequency analysis, and automatic detection of English text woven in. The latter half advances to the one-time pad, finding and generating primes, public-key key generation, and a programmed implementation of the RSA public-key algorithm, and an appendix on debugging Python code closes the book. About 330 pages and 475,000 characters, with sample source code and exercises at the end of each chapter, it suits a learn-by-typing approach.