Demystifying Cryptography with OpenSSL 3.0 (Alexei Khlebnikov)（Z-Library）

【One-Line Pitch】 A hands-on guide to using OpenSSL 3.0 for real network security work, moving from core cryptographic concepts to command-line and C code you can run. Best for developers, sysadmins, and DevOps engineers who want practical OpenSSL skills rather than pure theory. 【Book Arc】 - **Opening (~0%–10%)**: Introduces OpenSSL, its history, and what changed in 3.0, then frames the cryptographic building blocks—symmetric ciphers, modes, padding, and key generation—that later chapters depend on. - **Early (~10%–30%)**: Covers message digests and hash functions, MAC/HMAC and the Cryptographic Doom Principle, and deriving encryption keys from passwords, all with command-line and C examples. - **Middle (~30%–55%)**: Shifts to asymmetric cryptography—RSA encryption/decryption, digital signatures and verification, and the certificate concepts needed for TLS. - **Late (~55%–75%)**: Applies the foundations to TLS: building clients and servers, X.509 certificate verification, CRLs, OCSP, and client certificates. - **Ending (~75%–100%)**: Explores special TLS usages such as certificate pinning, non-blocking sockets, and non-standard sockets via BIOs, then walks through running a mini-CA for organizational PKI. 【Key Takeaways】 - **OpenSSL 3.0 is an architectural release, not just a feature release** (Opening): the provider concept and Apache 2.0 licensing are the headline changes, with more architectural work deferred to 4.0. - **Symmetric encryption choices matter more than the cipher name alone** (Early): block cipher modes, padding, and key generation are presented as a decision set, not isolated topics. - **Message digests underpin integrity, HMAC, signatures, and protocols** (Early): the book connects hashing to concrete uses like password verification, content identifiers, and proof-of-work. - **HMAC and encryption must be combined carefully** (Early): the Cryptographic Doom Principle warns against encrypt-then-MAC mistakes that break security. - **Passwords are not encryption keys** (Early): key derivation functions are necessary to turn human passwords into usable cryptographic keys. - **Asymmetric crypto solves key distribution but introduces trust problems** (Middle): man-in-the-middle attacks, fingerprints, key splitting, and trusted third parties are all framed as trust-establishment options. - **TLS is where the primitives become a working system** (Late): certificate verification, revocation via CRL/OCSP, and client certificates are shown through C programs. - **Running a mini-CA is a practical capstone** (Ending): generating root, intermediate, server, and client certificates ties the book’s concepts into an operational PKI workflow. 【Reading Tips】 - Deep-read the early chapters on symmetric encryption, digests, and HMAC; they are the vocabulary for everything later. - Skim the OpenSSL history and library-comparison material unless you need to justify a library choice; the practical value is in the code chapters. - Type and run the C examples rather than copying them—the book explicitly recommends this to avoid errors and build real familiarity. - Treat the TLS and mini-CA chapters as the payoff: read them with the earlier command-line examples nearby, since they combine multiple primitives. - Use the book as guidance, not a replacement for OpenSSL documentation; consult official docs or experiment when details are missing. 【Coverage Limits】 The excerpts cover the book’s structure, chapter topics, and stated audience, but do not include full technical explanations or code details from every chapter. Specific implementation nuances beyond the listed topics are not covered here.